Engine Lubrication System PDF

Presentation Title : Engine Lubrication System (Automotive Technology) Prepared by: 6th October stuff Internal Code: 2 Lubricating System Functions The main function of lubrication is to supply engin...

Presentation Title : Engine Lubrication System (Automotive Technology) Prepared by: 6th October stuff Internal Code: 2 Lubricating System Functions The main function of lubrication is to supply engine components with an adequate amount of oil with the correct pressure. Lubricate: to reduce energy losses and wear due to friction between moving parts. Cool: to protect engine parts from overheating since they can’t give off heat directly to the coolant or cooling air. Seal: to guarantee precision seal between engine moving parts, e.g. piston ring against cylinder wall. Clean: to remove abrasion, deposits and combustion residues or bind them in the oil to render them harmless to engine. Protect (engine) against corrosion. Damp engine noises: the lubricant layer has a noise and vibration damping effect 3 Pictures & Video Lubrication points Here are some of engine components that must be lubricated: Crankshaft bearings Connecting rod bearings Gudgeon pin bearings Tappets Camshaft bearings Cam tracks Rocker arms Timing chain Chain tensioners Cylinder barrels Exhaust gas turbocharger 5 Lubricating System Types Each of four stroke and two stroke engines have different types of lubricating system. For four stroke engines: 1. Forced-feed lubrication 2. Dry sump lubrication For two stroke engines: 1. Mixture lubrication 2. Total-loss lubrication We’ll study those used in four stroke engines in details. 7  Forced-Feed lubrication This is the most commonly used system e.g. tractors, trucks, automobiles. Working principle: a pump draws in oil supply from the oil pan through an oil strainer and forces it through pipes and lubricating passages to engine lubricating points, then oil drops off from these points and flows back to oil pan. Components: Oil pressure pump Oil suction pump Oil pan Oil filter Oil cooler Oil dipstick: check oil supply. Electric oil sensors: enable oil content and quality to be displayed in instrument panel. 8 9 Dry Sump Lubrication This is a special type of forced feed lubrication system. It’s commonly used in larger diesel engines like those of ships, also in gasoline engines used in racing cars and high-performance motorcycles. Working principle: the oil is directed by a suction pump to a separate oil reservoir instead of returning to oil pan, a pressurized oil delivery pump extracts oil from this reservoir and forces it to lubrication points via a filter and if necessary, an oil cooler. 10 11 Advantages of this type The oil pan in this type is flat, this reduces the engine height and vehicle’s center of gravity. Perfect lubrication is guaranteed in case of large engine inclinations e.g. off-road vehicles, motorcycles, curves taken in high speeds in sports cars. Better oil cooling due to isolated oil reservoir from engine and heat. Since dry sump lubrication is more expensive than forced feed lubrication, it is usually used only in low sports cars, off- road vehicles and motorcycles. 12 11.4.2 Engine lubrication components Lubrication components Oil pan Oil pump Oil filter Oil pressure gauge Oil cooler Oil pressure switch (indicator lamp) Pressure limiting valve Ventilation 14  Oil pan This holds the oil supply for the engine. The lowest point of the oil pan is frequently equipped with anti- rolling walls (baffle plates) which prevent the oil from flowing away from the suction point during the corners, acceleration and braking The surface of the oil pan also acts as a cooling surface for the oil 15 Oil pumps An oil pump must ensure an adequate oil pressure in combination with high delivery flow approx.(250 l/h to 350 l/h) Oil pump types: Gear pump Crescent pump Rotor pump 16 Gear pump Working principle In this type of pump the oil is carried in the tooth spaces and delivered along the inner pump wall to the other side The meshing of the teeth of the two gears prevents the oil from flowing back A vacuum pressure and overpressure are generated on the suction side and pressure side respectively 17  Crescent pump This is a special type of gear pump Working principle Its inner gear is usually seated directly on the engine crankshaft An outer gear mounted in the pump housing is arranged eccentrically to the inner gear. This creates a suction chamber and a pressure chamber which are separated from each other by crescent shaped spacer The oil is delivered in the tooth spaces along both the upper and lower sides of the crescent shaped spacer. Advantage of crescent pump over a conventional gear pump. Higher delivery rate, especially at low engine speeds 18  Rotor pump This consist of an internally toothed outer rotor and an external toothed inner rotor The inner rotor has one less tooth than the outer rotor and is connected to the drive shaft. Working principle The toothing of the inner rotor is shaped in such a way that each tooth touches the outer rotor and largely seals the chambers created As the rotors rotate the pump chambers on the suction side continually increases in size and the pump draws in oil The chambers on the pressure side decreases in size The oil forced by several narrowing pump cells into the pressure line so that the rotor pump operates uniformly Its able to generate high pressures with a high delivery flow 19 Rotor pump 20  Regulated rotor pump Design This has an additional control ring between the rotor ring and the pump housing which is turned depending on the oil pressure and the control spring. This pump enables the oil pressure to be kept constant irrespective of the engine operating conditions This results in constant lubricating conditions at all the lubrication points. 21 Regulated rotor pump Working principle Oil pressure too low : if the oil pressure drops below the limit pressure of for example 3.5 bar, the control spring can turn the control ring against the oil pressure This results in an increase in chamber size between the inner an the outer rotors In this way more oil is delivered from suction side to the pressure side and the oil pressure rises Oil pressure too high: if the oil pressure rises above the limit value. the oil pressure presses against the control ring and the control spring is compressed This result in a decreases in chamber size between the inner and outer rotors In this way ,less oil is delivered fro the suction side to the pressure side and the oil pressure drops 22  Oil pressure gauge, oil pressure indicator lamp These components serve to monitor the oil pressure, both are installed between the oil pump the bearings Oil pressure gauge This allows the current oil pressure to be read off directly A pressure sensor is required in the pressure line after the oil pump for pressure measurement. 23 Oil pressure switch (indicator lamp) Function This goes out during engine operation and indicates to the driver whether there is sufficient oil pressure available in the system Working principle If the oil from the pressure line presses on the switching contact body, the earth/ground contact for the oil pressure indicator lamp is interrupted and the lamp goes out. 24 Pressure limiting valve This connected downstream of the oil pump and prevent excessive oil pressure (> approx. 5 bar ) High pressure oil is not always proof of good lubrication Oil pressure will also be high but lubrication poor when an oil line or filter is clogged Excessively high oil pressure poses a risk to seals, oil lines and oil hoses to the oil cooler and oil filter 25  Oil filter Function These are installed to prevent premature deterioration of the lubricant oil caused by solid impurities e.g. metal abrasion, soot, dust particles Oil filters however are unable to remove liquid contaminants or contaminants dissolved in the oil. Filter types: Full-flow oil filter Partial-flow/bypass oil filter 26  Full-flow oil filter Full-flow oil filtering ensures that unfiltered oil cannot reach the lubrication points In order to facilitate an adequate throughput of oil It is important that the flow resistance of the filter(bore size) not to be high This would limit the filter effect, tiny contaminants would not be filtered out of the oil 27 28  Overflow valve Overflow valve Working principle If the filter is clogged the oil can flow unfiltered through the overflow valve past the filter to the lubrication points. 29  Return check valves Return check valves Working principle These can additionally be installed in the filter inlet and outlet lines to prevent the full-flow oil filter from running dry when the engine is stopped 30  Crankcase ventilation Spark ignition engines and in particular turbocharged diesel engines are subjected to blow-by gases Which enter the crankcase from the combustion chamber This gas which is contaminated by superfine oil droplets, fuel residues, water vapor and soot is returned to the engine intake air via an oil separator 31  Engine oil The most important engine oil property is that its viscosity changes with temperature and low freezing point. So, we find that: Higher oil pressure when the engine is cold. (Engine oil is cold and at higher viscosity) lower oil pressure when the engine is at normal operating temperature. (Oil becoming thinner) Because of oil pumps, lower oil pressures at idle and higher pressures at higher engine speeds Viscosity: serves as an index of an oil’s flow properties by quantifying its internal friction Highly-fluid, free flowing oils have a low viscosity and corresponding low resistance to displacement forces While high viscosity oil exhibit higher flow resistance this resistance that the fluid displays against the mutual displacement of two contiguous layers is also referred to as internal friction (shear stress) 32 33  Engine oil types Base oils (mineral oils ): For use in engines and gearboxes are produced by vacuum distilling the residual materials remaining after atmospheric distilling of crude oil The long-chained hydrocarbon molecules contained in lubricating oils are sensitive to heat Selected additives are employed to endow the base oils with the desired properties in areas such as anti-oxidation protection and viscosity Hydrocarbon base oils ( synthetic oils): Synthetic oil is a man-made lubricant that consist of artificially made chemical compounds synthetic oils are typically made of chemically modified materials such as petroleum components but the base material always crude oil 34  Engine oil specification SAE viscosity grades: This classification system has been defined by the American society of Automotive Engineers to assist in selecting engine and gearbox oils for use under various climatic condition A distinction is made between single-grade oils such as SAE 10W, SAE 20W/20 ( winter oils ) SAE 30, SAE 50 ( summer oils ) Multigrade oils such as SAE 15W-50 for year-round use The SAE classes start at 0 W and end at 50. Higher numbers correspond to thicker oil 35 36  Oil additives Chemical additives are used due to the fact that base oils cannot satisfy the multiplicity of demand placed on engines and gear lubricants Additives improves oil characteristics 37 Engine oil classification system 38  Stresses of lubricant oils Oil ageing Oil sludging Oil dilution Oil thickening Oil consumption 39 Maintenance, problems and troubleshooting 40  REFERENCES: Automotive technology principles, diagnosis, and service fourth edition. 41