Lubrication

LUBRICATION SYSTEMS

DEF OF LUBRICATION

Lubrication is an art of admitting a lubricant between two surfaces that are in contact and in relative motion.

PURPOSE OF LUBRICATION

To reduce friction and wear between moving parts and there by the energy loss and to increase the life of the engine.

To cool the surfaces by carrying away the heat generated in the engine components

To provide sealing action i.e. the lubricating oil helps the piston rings to maintain an effective seal against the high pressure gases in the cylinder from leaking out into the crankcase.

To clean the surfaces by washing away carbon and metal particles caused by wear.

MAIN COMPONENTSIn a reciprocating engine there are many surfaces in

contact with each other…..

Main crankshaft bearings

Big end bearings

Gudgeon pin bearings

Piston rings and cylinder walls

Timing gears

Camshaft and camshaft bearings

Valve mechanism

REQUIREMENTS OF LUBRICANTS Viscosity Physical stability Chemical stability Resistance against corrosion Pour point Flash point cleanliness Resistance against extreme pressure

TYPES OF LUBRICANTS Animal oils Vegetable oils Mineral oils Synthetic lubricants Greases Solid lubricants

TYPES OF LUBRICATION SYSTEMS

Petroil lubrication system

splash lubrication system

pressure lubrication system

Dry lubrication system

PETROIL LUBRICATION SYSTEM Generally used for small 2-stroke engines.

Simplest of all types.

Certain amount of lubricating oil is mixed with petrol; usually the ratio is 2%-3%.

Due to high temperatures in the crank case, the petrol component vaporizes leaving a thin film of lubricating oil on the crank case, cylinder bearings, crankshaft and bearings

SPLASH LUBRICATING SYSTEM Employed for the engines of early motor cycles.

One of the cheapest method.

A scoop is made in the lowest part of the connecting rod and the oil is stored in the oil trough.

When the engine runs, the scoop causes the oil to splash on the cylinder walls, each time it passes through its BDC position.

This affects the lubrication of engine walls, gudgeon pin, main crankshaft bearings, big end bearings.

PRESSURE LUBRICATION SYSTEM This system used in almost universally in modern cars

engines.

An oil pump takes the oil from the wet sump .

Delivers it through a filter to the main oil gallery at a pressure of 200 to 400 kpa.

During its circulation, the oil gains heat from the various engine parts, which is given out to the sump walls.

DRY-SUMP LUBRICATION SYSTEM Mainly employed for racing car engines where they has to

operate at very steep angles.

Contains two pumps instead of one.

Scavenge pump installed in the crankcase which pumps oil to a separate reservoir.

From that, oil is pumped by a pressure pump through a filter to the cylinder bearings.

The oil pressure is maintained at 400-500 kpa for the big end bearings while about 50-100 kpa pressure is used for timing gears and camshaft bearings.

OIL STRAINERS Oil strainer is attached at the inlet of the oil pump to

guard it against the entry of grit etc.,

It is made of ordinary wire mesh screen.

OIL PUMPS Its function is to supply oil under pressure to the

various engine parts.

It is generally located inside the crankcase below the oil level.

Driven from the end of the distributor shaft.

OIL FILTERSUsed for removing the sludge and fine carbon

particles due to metal wear, especially during the running period, particles of rust formed in the engine contaminates the oil.

TYPES CARTRIDGE TYPE

EDGE TYPE

FUNCTION The function of the ignition system is to produce a

spark in the engine cylinder towards the end of the compression stroke

REQUIREMENTS It should provide a good spark between the

electrodes at the correct time.

It should function efficiently over the entire range of engine speed.

It should be light, effective and reliable.

It should be compact and easy to maintain.

It should be cheap and convenient to handle.

The interference from the high voltage should not affect the functioning of the radio and television receivers inside an automobile

TYPES OF IGNITION systemsBattery ignition system.

Magneto ignition system.

Transistorized coil ignition system.

Capacitive discharge system.

BATTERY IGNITION SYSTEM Also called as an storage device. Ignition coil is the source of ignition energy. Coil stores the energy in the form of magnetic field

and delivers it at the instant of ignition in the form of surge of high voltage current through the high tension cables.

Storage of energy in the magnetic field is based on the inductive process.

Consists of two coils of wire, one wound around the other.

Called as PRIMARY and SECONDARY windings.

MAGNETO IGNITION SYSTEM It is a special type of ignition system. With its own electric generator it can provide the

necessary energy for the system. It replaces all the components of the coil ignition

system except the spark plug. The magneto when rotated by the engine is capable

of producing a very high voltage.

layout

TRANSISTORIZED COIL IGNITION SYSTEM Also called as high energy electronic systems.

Provide a high voltage.

Use electronic triggering to maintain the required timing.

The cam assembly and the contact breaker are replaced by a magnetic pulse generating system.

It detects the distributor shaft position and sends electrical pulses to an electronic control module.

The module switches off the current flow to the primary coil, inducing a high voltage in the secondary winding.

This voltage is supplied to the spark plugs.

CAPACITVE DISCHARGE IGNITION system Capacitor is used rather than an induction coil to store

the ignition energy.

The capacitance and charging voltage of the capacitor determine the amount of stored energy.

The ignition transformer steps up the primary voltage to the high voltage required.

The CDI trigger box contains the capacitor, thyristor power switch, charging device to convert the battery low voltage to the charging voltage of 300v to 500v.

The advantage of using this system is that it is insensitive to electrical shunts resulting from the spark plug fouling.

Spark is strong but short.