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 COMPONENTS
In 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 FILTERS
Used 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.

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 systems
 Battery 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.

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.

Lubrication

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