Govindaraju'H'K' Assistant Professor and Head, Department of Automobile Engg', S J M Institute of Te

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Govindaraju.H.K.Assistant Professor and
Head,Department of Automobile Engg.,S J M
Institute of Technology,Chitradurga 577
502.e-mail anchith_g_raj_at_yahoo.co.inSubject
Theory and Design of Automotive
Engines Sub Code - AU51 V
Semester, Automobile Engineering

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Topics covered on (18-09-07)
Piston function and characteristics Piston
materials Material properties Piston
clearance Piston lubrication Types of pistons
Topics covered on (19-09-07)
Piston temperature distribution Piston
manufacture Piston heat treatment process,
piston rings
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Today's topics
Compression rings, types Oil rings, types Heat
treatment of rings Ring collapse Piston pin
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
4

Functions of compression ring

• Compression ring closes the gap between the
  pistons
• outside wall and the cylinder wall,

• The compression ring further exerts a side
  pressure
• (horizontal arrow)on the cylinder wall in
  addition to its elastic
• forces.

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Types of compression rings or Gas rings.
A Chamfered, B Tapered,
C Side grooved
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Functions of Oil- ring

• The primary purpose of the oil ring is to
  prevent oil
• from leaking into the combustion chamber.

• Excess oil is scraped from the cylinder wall.
  Openings
• in the Piston wall direct oil back into the
  engines crankcase

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Piston ring Manufacture
Ring

Pot form which Rings are cut

• Pot Casting (Centrifugal casting) i.e. from long
  cylinder casting
• Close grain structure
• By turning and boring the rings are cut on a
  lathe, finished by
• grinding process.

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Individual Casting of rings
Ring
Method of manufacturing Individual ring

• No of rings are produced in a single casting
  individually
• Rough on the inside but Denser material and more
• springing nature

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
10
Heat treatment of piston rings
Anti-scuff coating Molybdenum Anti-abrasion
coating Chromium
How to choose piston rings
Slightly scored walls plane cast iron
rings Rebored cylinders Chrome rings Good
conditioned engines Molybdenum rings
Ring collapse and blow by of gases
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Piston pin Function Methods of
fixing Piston pin materials Design
analysis, Methods of manufacture
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Piston pin

• Piston pin or gudgeon pin or wrist pin connects
  the piston
• and the small end of the connecting rod.
• Piston pin is generally hollow. and made
  from case
• hardening steel heat treated to produce a
  hard wear
• resisting surface

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Requirements of piston pin

• Adequate rigidity to keep stressing of the
  piston pin bore
• this rigidity consists of bending deflection
  and ovalization.
• Adequate rigidity to provide uniform bearing
  loads in pin
• bore area.
• Sufficient bearing area from the length and
  diameter to keep
• bearing pressure in the piston pin bore and
  connecting rod
• bore at an acceptable level.

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Requirements of piston pin Contd

• Light in weight to reduce the effects of inertia
  forces.
• Good outer diameter and surface finish enhancing
• lubrication with piston and connecting rod
  mating surfaces.
• Adequate material and heat treat to provide
  structural
• strength and good wear characteristics

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Methods of connecting piston pin

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Production of piston pin Tubular stock of
Case hardened Finished by grinding or center
less grinding Do1.4d for CI Do1.5d for
Al Bosses are slightly tapered
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Piston pin offset
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Lubrication of piston pin
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Outer diameter of pin (based on bearing) Outer
diameter of piston pin is calculated based on
bearing pressure length of gudgeon pin bearing
0.45D to 0.5 Bearing pressures for
different engines (MPa) For gas engines
12.4 For oil engines 15 For automotive
engines 15.7
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Inner diameter of pin (based on
bending) Considering bending stress due to gas
load Bending stress due to gas
load Where M The pin inner diameter
Z
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga