Internal combustion engine consists of a number of parts which are given as follows: 1. Cylinder 2. Cylinder Block 3. Cylinder Head 4. Cylinder Liner or Sleeve 5. Piston 6. Piston Ring 7. Piston Pin 8. Connecting Rod 9. Crankshaft 10. Flywheel 11. Crankcase 12. Camshaft 13. Timing Gear 14. Inlet Manifold 15. Exhaust Manifold.
Component # 1. 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.
Component # 2. Cylinder Block:
It is the solid casting which includes the cylinder and water jackets (cooling fins in the air cooled engines).
Component # 3. Cylinder Head:
It is a detachable portion of an engine which covers the cylinder and includes the combustion chamber, spark plugs and valves.
Component # 4. 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 liners 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.
Liners are classified as:
(а) Dry Liner – It makes metal to metal contact with the cylinder block casting and
(b) Wet Liner – It comes in contact with the cooling water, whereas dry liners do not come in contact with the cooling water.
Component # 5. Piston:
It is a cylindrical part closed at one end which maintains a close sliding fit in the engine cylinder. It 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. Cast iron is chosen due to its high compressive strength, low co-efficient of expansion, resistance to high temperature, ease of casting and low cost. Aluminum and its alloys are preferred mainly due to its lightness.
Head (Crown) of Piston:
It is the top of the piston.
Skirt:
It is that portion of the piston below the piston pin which is designed to absorb the side movements of the piston.
Component # 6. 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 functions of the ring are as follows:
(i) It forms a gas tight combustion chamber for all positions of piston.
(ii) It reduces contact area between cylinder wall and piston wall for preventing friction losses and excessive wear.
(iii) It controls the cylinder lubrication.
(iv) 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 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.
Component # 7. Piston Pin:
It is also called Wrist pin or Gudgeon pin.
Piston pin is used to join the connecting rod to the piston. It provides a flexible or hinge like connection between the piston and the connecting rod. It is usually made of case hardened alloy steel.
Component # 8. Connecting Rod:
It is special type of rod, one end of which is attached to the piston and the other 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 bushing and big end is provided with bearings, split into two shells.
Component # 9. Crankshaft:
It is the main shaft of an engine which converts the reciprocating motion of the piston into rotary motion of the flywheel. Usually the crankshaft is made of drop forged steel or cast steel. The space that supports the crankshaft in the cylinder block is called main journal, whereas the part to which connecting rod is attached is known as crank journal.
Crankshaft is provided with counter weights throughout its length to have counter balance of the unit. Split shell bearings are mostly used as main bearings of the crankshaft. Crankshaft is subjected to bending as well as twisting from the connecting rod end.
Component # 10. Flywheel:
Fly wheel is made of cast iron.
Its main functions 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) It also carries ring gear that meshes with the pinion of starting motor.
c) The rear surface of the flywheel serves as one of the pressure surfaces for the clutch, plate.
d) Engine timing marks are usually stamped on the flywheel, which helps in adjusting the timing of the engine.
e) Sometime the flywheel serves the purpose of a pulley for transmitting power.
Component # 11. 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 such accessories as the oil pump, oil filter, generator, starting motor and ignition 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.
Component # 12. 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 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.
Component # 13. 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 on 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 valves as well as fuel injection timing.
Component # 14. 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.
Component # 15. 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.