Lubrication used For Internal Combustion Engine
Since frictional forces causes wear and tear of rubbing parts of the engine and thereby the life of the engine is reduced. So the rubbing part requires that some substance should be introduced between the rubbing surfaces in order to decrease the frictional force between them. Such substance is called lubricant. The lubricant forms a thin film between the rubbing surfaces. And lubricant prevents metalto-metal contact. So we can say “Lubrication is the admission of oil between two surface having relative motion”.
|Lubrication System Basic (Image Source: Slideshare.com)|
The main function of lubricant is to,
1. To reduce friction and wear between the parts having relative motion by minimizing the force of friction and ensures smooth running of parts.
2. To seal a space adjoining the surfaces such as piston rings and cylinder liner.
3. To clean the surface by carrying away the carbon and metal particles caused by wear.
4. To absorb shock between bearings and other parts and consequently reduce noise.
5. To cool the surfaces by carrying away heat generated due to friction.
6. It helps the piston ring to seal the gases in the cylinder.
7. It removes the heat generated due to friction and keeps the parts cool.
The various parts of an engine requiring lubrication are;
1. Cylinder walls and pistons.
2. Main crankshaft bearings.
3. Piston rings and cylinder walls.
4. Big end bearing and crank pins.
5. Small end bearing and gudgeon pin bearings.
6. Main bearing cams and bearing valve tappet and guides
7. Timing gears etc.
8. Camshaft and cam shaft bearings.
9. Valve mechanism and rocker arms.
A good lubricant should possess the following properties:
1. It should not change its state with change in temperature.
2. It should maintain a continuous film between the rubbing surfaces.
3. It should have high specific heat so that it can remove maximum amount of heat.
4. It should be free from corrosive acids.
5. The lubricant should be purified before it enters the engine.
6. It should be free from dust, moisture, metallic chips, etc.
7. The lubricating oil consumed is nearly 1% of fuel consumption.
8. The lubricating oil gets heated because of friction of moving parts and should be cooled before re-circulation.
TYPES OF LUBRICANTS:
Lubricants are at following three types.
1. Solid: graphic, mica etc
2. Semi solid: grease
3. 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.
Grade of lubricants:
- Generally lubricating oils are graded by their SAE ( society of automotive engineers) viscosity no.
- 5w,10w,20w SAE no. lubricating oil are for winter use.
- 20,30,40 SAE no. lubricating oil are for summer use.
- Lubrication System: It is the system by means of which various engine parts are lubricated.