LUBRICATION SYSTEM OF INTERNAL COMBUSTION (I.C) ENGINE

INTRODUCTION

we stand and walk on our feet due to friction but coin has two sides similarly friction is our friend and enemy both.wherever relative motion takes place friction come into consideration 

and this happens in our engines

The frictional force developed in an I.C.Engine which consists of no. of sliding & rotating components like bearings, pistons, valve gears etc may be so large that it may cause excessive wear & tear due to which replacement of components is very necessary. A large amount of the power developed by the engine may also be used to overcome this force of friction. Due to friction, heat is also generated. Due to generation of heat, the temp. of various components may rise to so high a value that a complete seizure of the engine components may take place.
Therefore, in order to overcome these difficulties, a thin film of a suitable lubricant is interposed where the metal-metal contact takes place. This thin film reduces the friction considerably by keeping the two metal surfaces apart from each other and thus wear, tear & temp. developed are also reduced greatly.

LUBRICATION
To supply lubricating oil between the moving parts is simply termed as “lubrication”.
Purpose of Lubrication
1. To reduce friction between the moving parts to a minimum value, thereby to reduce power loss due to friction.
2. To minimize wear of moving parts as far as possible.
3. To provide cooling effect by acting as a cooling medium & remove heat from various parts.
4. To form an effective seal between the piston rings & cylinder walls and thus prevent the escape of gases from the cylinder and avoid power loss.
5. To keep the engine parts clean by washing off and carrying away the impurities from the engine parts.
6. To provide cushion (protection) to the engine by absorbing the shocks developed by sudden application of load and instant combustion of fuel in the cylinder of the engine.
7. To reduce noise by absorbing shocks between the bearings and engine parts.
8. To prevent metallic components from corrosive attack by the acid formed during the combustion process.

TYPES OF LUBRICANTS:

Lubricants are at following three types.1. Solid: graphic, mica etc2. Semi solid: grease3. Liquid: mineral oil, vegetable oil, animal oil etc.

•  Graphite is often mixed with oil to lubricate automobile spring. Graphite is also used as a cylinder lubricant.
•  Grease is used for chassis lubrication.
•  Mineral oils are almost used for engine lubrication.

Properties of Lubricant

1. high boiling point and low freezing point (in order to stay liquid within a wide range of temperature)
2. high viscosity index.
3. thermal stability.
4. hydraulic stability.
5. demulsibility.
6. corrosion prevention.
7. high resistance to oxidation.

Engine Lubrication System: Engine lubrication system is mainly of following types.

1. Splash system
2. Pressure system
3. Petroil system or mist lubrication

splash system:-In this system of lubrication the lubricating oil is stored in an oil sump. A scoop or dipper is made in the lower part of the connecting rod. When the engine runs, the dipper dips in the oil once in every revolution of the crank shaft, the oil is splashed on the cylinder wall. Due to this action engine walls, piston ring, crank shaft bearings are lubricated.

pressure system:- In this system of lubrication, the engine parts are lubricated under pressure feed. The lubricating oil is stored in a separate tank (in case of dry sump system) or in the sump (in case of wet sump system), from where an oil pump (gear pump) delivers the oil to the main oil gallery at a pressure of 2-4 kg/cm2 through an oil filter.

The oil from the main gallery goes to main bearing, from where some of it falls back to the sump after lubricating the main bearing and some is splashed to lubricate the cylinder walls and remaining goes through a hole to the crank pin. From the crank pin the lubricating oil goes to the piston pin through a hole in the connecting rod, where it lubricates the piston rings.
For lubricating cam shaft and liming gears the oil is led trough a separate oil line from the oil gallery.
The oil pressure gauge used in the system indicates the oil pressure in the system. Oil filter & strainer in the system clear off the oil from dust, metal particles and other harmful particles.

petroil system:-

This type of lubrication is used for two stroke cycle engines. The lubrications oil (2 to 3 percent) is mixed with petrol in the fuel tank. The oil and fuel mixture is inducted through the carburetor. Petrol gets evaporated and the oil lubricates the main parts of the cylinder.

The fuel -oil ratio used is important for good performance. the optimum fuel -oil ratio used is 50:1.

ADVANTAGE

• Separate lubricating system is not needed.
• No maintenance cost for lubriction system.
• Weight of engine is reduced by avoiding separate lubricating system.

DISADVENTAGE

• If oil is less there is chance for seizure of engine.

More oil makes excess smoke in the exhaust.

CONCLUSION:

We often think that the function of lubricating oil is only to lubricate the engine parts so that the power loss due to friction is minimum. But a lubricating oil has many other functions which are explained before.
Lubrication must be done properly and right type of lubricant should be used. Improper or inadequate lubrication of engine will cause serious trouble such as scored cylinders, worn or burnt out bearing, misfiring cylinders, dirty spark plug, stuck piston rings, engine deposits and sludge and excessive fuel consumption.