Components of Engine

Components of Engine
    The internal combustion engine consists of the following engine components:
    Cylinder
    • It is a part of the engine which confines the expanding gases and forms the combustion space.
    • It is the basic part of the engine. It provides space in which piston operates to suck the air or air-fuel mixture.
    • The piston compresses the charge and the gas is allowed to expand in the cylinder, transmitting power for useful work.
    • Cylinders are usually made of high grade cast iron.
    Cylinder block
    • It is the solid casting which includes the cylinders and water jackets in case of water cooled engines. (cooling fins in the air cooled engines).
    • Slated on engine and its components.
    Cylinder head
    • It is a detachable portion of an engine which covers the cylinder and includes the combustion chamber, spark plug/atomizer and valves.
    Cylinder liner or sleeve
    • It is a cylindrical lining either wet or dry which is inserted in the cylinder block in which the piston slides.
    • Cylinder liner are fitted in the cylinder bore and they are easily replaceable.
    • The overhauling and repairing of the engines, fitted with liners is easy and economical.
    • The cylinder liners are classified as : (a) Dry liner and (b) Wet liner.
    • The dry liner makes metal to metal contact with the cylinder block casing and do not come in contact with the cooling water.
    • The wet liners come in contact with the cooling water.
    Piston
    • It is a cylindrical part closed at one end and open at the other end, which maintain a close sliding fit in the engine cylinder.
    • The piston is shown in Plate 2.5. The piston is connected to the connecting rod by a piston pin.
    • The force of the expanding gases against the closed end of the piston, forces the piston down in the cylinder.
    • This causes the connecting rod to rotate the crankshaft connected rod is made of cast-iron.
    • Cast iron is chosen due to its high compressive strength, low coefficient of expansion, resistance to high temperature, ease of casting and low cost.
    • Aluminum and its alloys preferred mainly due to it lightness and easy dissipation of heat.
    2.9
    Plate : 2.5 Piston
    Head (Crown) of piston
    • It is the top portion of the piston where the grooves are provided for inserting the piston rings and oil rings..
    Skirt
    • It is that portion of the piston below the piston pin which is designed to absorb the side movements of the piston.
    Piston ring
    • It is a split expansion ring, placed in the groove of the piston. Piston rings are fitted in the grooves, made in the piston. They are usually made of cast iron or pressed steel alloy.
    The function of the ring are as follows :
    a) It forms a gas tight combustion chamber for all positions of piston.
    b) It reduces contact area between cylinder wall and piston wall preventing friction losses and excessive wear.
    c) It controls the cylinder lubrication.
    d) It transmits the heat away from the piston to the cylinder walls.
    Piston rings are of two types :
    (a) Compression ring and
    (b) Oil ring
    a. Compression ring : Compression rings are usually plain, single piece and are always placed in the grooves, nearest to the piston head.
    b. Oil ring: Oil rings are grooved or slotted and are located either in the lowest groove above the piston pin or in a groove above the piston skirt. They control the distribution of lubrication oil in the cylinder and the piston. They prevent excessive oil consumption also. Oil ring is provided with small holes through which excess oil returns back to the crankcase chamber. Ring clearance is the gap at the joint of the ring, measured when the ring is inside the cylinder. The gap is usually 1 mm per 200 mm diameter of the piston. This clearance is necessary for expansion of the ring in heated condition, without which the ring can break or buckle. The piston ring and oil ring are shown in Plate 2.6.
    2.10
    Plate : 2.6 Piston ring and oil ring
    Piston Pin
    • It is also called as wrist pin or gudgeon pin. Piston pin is used to join the small end of the connecting rod to the piston.
    • The piston pin is shown in Plate 2.7. It provides a flexible or hinge like connection between the piston and the connecting rod.
    • It is usually made of case hardened alloy steel.
    2.11
    Plate 2.7 Piston pin
    Connecting rod
    • It is special type of rod, small end of which is attached to the piston and the larger end to the crankshaft.
    • It transmits the power of combustion to the crankshaft and makes it rotate continuously.
    • It is usually made of drop forged steel. Its small end is fitted with bronze busing and big end is provided with split bearings.
    2.12
    Plate : 2.8 Connecting rod
    Crankshaft
    • It is the main shaft of an engine which converts the reciprocating motion of the piston into rotary motion of the flywheel.
    • The crankshaft of a four cylinder engine is shown in Plate 2.9. Usually the crankshaft is made of drop forged steel or cast steel.
    • Crankshaft is provided with counter weights throughout its length to have counter balance of the unit.
    • Split shell bearings are used as main bearings of the crankshaft. Crankshaft is subjected to bending as well as twisting from the connecting rod end.

    2.13
    Plate : 2.9 Crankshaft of a four cylinder engine
    Flywheel
    Flywheel is made of cast iron.
    The main functions of the flywheel are as follows:
    a) It stores energy during power stroke and returns back the same energy during the idle strokes, providing an uniform rotary motion by virtue of its inertia.
    b) The rear surface of the flywheel serves as one of the pressure surfaces for the clutch plate.
    Engine timing marks are usually stamped on the flywheel, which helps in adjusting the timing of the engine. Two views of the flywheel are shown in plate 2.10.
    2.14
    Plate : 2.10 Two views of the fly wheel
    Crankcase
    • The crankcase is that part of the engine which supports and encloses the crankshaft and camshaft.
    • It provides a reservoir for the lubricating oil of the engine.
    • It also serves as a mounting unit for accessories as like oil pump, oil filter, dynamo, self motor and other components.
    • The upper portion of the crankcase is usually integral with cylinder block.
    • The lower part of the crankcase is commonly called oil pan and is usually made of cast iron or cast aluminum.
    • The crankcase of a four cylinder engine is shown in plate 2.11.
    2.15
    Plate : 2.11 Crankcase of four cylinder engine
    Camshaft
    • It is a shaft which raises and lowers the inlet and exhaust valves at proper time.
    • Camshaft is driven by crankshaft by means of gears, chains or sprockets.
    • The camshaft of a four cylinder, four stroke engine is shown in Plate 2.12.
    • The speed of the camshaft is exactly half the speed of the crankshaft in four stroke engine.
    • Camshaft operates the ignition timing mechanism, lubricating oil pump and fuel pump.
    • It is mounted in the crankcase, parallel to the crankshaft.
    2.16
    Plate : 2.12 Cam shaft of a four cylinder engine
    Timing gear
    • Timing gear is a combination of gears, one gear of which is mounted at one end of the camshaft and the other gear at the end of the crankshaft.
    • Camshaft gear is bigger in size than that of the crankshaft gear and it has twice as many teeth as that of the crankshaft gear.
    • For this reason, this gear is commonly called half time gear.
    • Timing gear controls the timing of ignition, timing of opening and closing of valve as well as fuel injection timing.

    2.17
    Plate : 2.13 A view of timing gear and chain arrangement
    Inlet manifold
    • It is that part of the engine through which air or air-fuel mixture enters into the engine cylinder.
    • It is fitted by the side of the cylinder head.
    Exhaust manifold
    • It is that part of the engine through which exhaust gases go out of the engine cylinder.
    • It is capable of withstanding high temperature of burnt gases.
    • It is fitted by the side of the cylinder head.

    The different parts of piston and engine parts along with their position in the engine are shown in Plates 14 and 15.
    2.18
    Plate : 3.14 Different parts of the piston



    2.19
    Plate : 2.15 Different parts of the engine
    (Source: http://www.aa1car.com
Last modified: Tuesday, 26 June 2012, 7:46 AM