3. INTRODUCTION : PISTON IS ONE
OF THE MAIN PART OF ENGINE.
WHICH IS SUBJECTED TO
ENORMOUS THRUST CAUSED BY
BURNING OF FUEL AND
TRANSMITTING THIS THRUST TO
THE ROTARY MOTION OF CRANK
SHAFT. THESE ARE MOSTLY MADE
OF ALUMINUM ALLOY. TO
4. AIM :
(1) PROVIDES CLOSED CHAMBER
TO GASES TO BURN.
(2) SUCKS AIR DURING SUCTION
STROKE.
(3) COMPRESS AIR DURING
COMPRESS STROKE.
(4) IT A MEDIUM TO TRANSFER
HEAT ENERGY TO CRANK
5. FUNCTION OF PISTON :
(1) WHEN THE PISTON MOVES FORM
TDC TO BDC IN SUCTION STROKE IT
PRODUCES A PARTIAL VACUUM DUE
TO WHICH FRESH CHARGE IS SUCKED
IN I.E WORKS AS PUMP FOR TAKING
AIR IN THE CYLINDER.
(2) SOME OF THE PISTON HAVE
COMBUSTION CHAMBER MADE IN
6. PRODUCED IN THE POWER STROKE
TO CRANK SHAFT.
(4) IN EXHAUST STROKE IT PUSHED
OUT EXHAUST GASES.
(5) IT WORK AS A GUIDE FOR THE
UPPER PART OF CONNECTING
ROD.
(6) IT CARRIES RING WHICH SEAL
COMBUSTION FROM SUMP.
7. PARTS OF PISTON
(A) HEAD
(B) SKIRT
(C) RING GROOVE
(D) RING LAND
(E) GUDGEON PIN BOSS
9. Piston Construction
Piston head
– Round
– Approx. .040 undersized
Ring grooves
Ring lands
Drain holes and slots
Wrist pin boss
10. HEAD : IT IS THE UPPERMOST PARTS OF
PISTON WHICH IS SUBJECTED TO HOT
BURNING GASES WITH TEMPERATURE
AND PRESSURE.
SKIRT : SKIRT OF LOWER PART OF
PISTON AND WORKS AS A GUIDE FOR
THE PISTON SO THAT IT MOVES
STRAIGHT IN THE CYLINDER.
RING GROOVE : GROOVE ARE MADE IN
THE PISTON TO ACCOMMODATE
COMPRESSION AND OIL RING GROOVE
11. RING LAND : THE SPACE LEFT IN THE
CIRCUMFERENCE OF PISTON AFTER CUTTING
RING GROOVE IS CALLED RING LAND.
GUDGEON PIN BOSS : THE PLACE WHERE
GUDGEON PIN IS FIXED IN THE PISTON IS
KNOWN AS GUDGEON PIN BOSS AND IS
USUALLY REINFORCED.
THIS IS ALSO KNOW AS WAIST PIN AND IS
USED TO CONNECT PISTON WITH
CONNECTING ROD. IT IS MADE OUT OF STEEL
ALLOY AND HOLLOW FROM INSIDE SO THAT
IT IS LIGHT WIGHT AND AT THE TIME,
12. CLEARANCE OF PISTON : FOR
THE COST IRON PISTON KEEP
CLEARANCE 0.0007” (0.018 MM)
PER INCH DIA. OF PISTON AND
FOR ALUMINUM ALLOY PISTON
KEEP 0.001” (0.025 MM) PER
INCH DIA OF PISTON.
13. PISTON RING : PISTON RING ARE
USED IN PISTON TO MAINTAIN
GAS TIGHT SEAL BETWEEN THE
PISTON AND CYLINDER. PISTON
RING MOSTLY MADE OUT OF
CAST IRON.
PISTON RING IS TWO TYPE.
(A) COMPRESSION RING
14. Piston Construction
Materials
– Cast iron (used in very old engines)
– Cast aluminum (most common)
– Forged aluminum
– Hypereutectic alloys (high silicon content
aluminum)
– Carbon Graphite (being tested)
15. Piston Construction
Piston Pin Offset
– The piston pin is offset towards the major thrust
side of the piston to reduce piston wear, and
piston noise
– The major thrust side is the side that is loaded
during the power event
– The minor thrust side is the side loaded during
the compression event
