Evaluation of Cam and Tappet Wear

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Contents

• Introduction• Valve train Configurations• Engine Valve train wear• Three modes of Lubrication• Design and fabrication of fixture for LVDT• Design and fabrication of fixture for Tappet• Tappet Wear Analysis software• Testing and Experimentation procedure• Results• References 2

INTRODUCTION

Drivers of Engine Technology:

Durability

Fuel Economy

Emissions

Exotic Coatings

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How they are inter-related…?

Fuel Economy

Emissions

Low viscosity oil e.g. 5W30,0W20

Low SAPSCatalytic Converter

Durability

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Valve train Configurations

Widely used configuration

Direct Actinge.g. Mercedes Benz OM646

End pivoted Roller Follower

e.g. Toyota Prius

Centrally pivoted Roller Follower

e.g. BMW

Push rod Rocker Arm

e.g. Cummins B

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Engine Valve train Wear

Valve train

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Three modes of Lubrication

• Hydrodynamic• Mixed• Boundary

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30o

Design of Fixture for Tappet

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Locking Legs

Jiggle pin locking hole

Overall height is 5mm less than tappet’s height.

Design of Fixture for LVDT

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90o V-Block Centralizer

Teflon Screw

Sliding Contact Points

Spring Washers

Software for Tappet Wear Analysis

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0.036

Testing and Experimentation Procedure

• Alignment of test rig• Flushing• Pour Group IV oil• Heating oil at 80 oC

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Oil Tank

Oil Pump

Motor

Control Unit

Cylinder Head

Heating and Cooling Unit

Plate Heat Exchanger

• Maintaining oil pressure at 1.8 bar• Measure initial cam lift• Start motor and maintain 500 RPM• Run test for 24 hours• Measure Cam lift using LVDT and record any

variation

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2-3 microns difference recorded in cam lift over the same

point for CW and CCW rotation.

Hysteresis

• Scan the tappets using 2-D profilometer• Use Tappet Analysis Software to measure wear

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Test Rig Schematic Diagram

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Tappet

Oil Tank

Results

Wear burns showing excessive wear on sides.

Measured wear 27 microns.

Most of the wear occurs within 30o

periphery of cam nose.

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Oil film is trapped

between cam and

tappet at centre

and solidifies due

to high pressure.

Tappet Wear Analysis

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0.036

Measured wear 36 microns.

2014 2015Sept Oct Nov Dec Jan Feb Mar Apr May June July

Start 10/9/2014 Finish

15/7/2015

5 Weeks Project Selection

10 Weeks Literature Review

8 Weeks Design of JIG

5 Weeks

1 2 3 4 5 6 7 8 109 11 1312 141516 17 18 252019 26 2827 29 30 31 3332 3424232221 35 36 37 38 39 40 41 4442 43

Design of Overhead Assembly

6 Weeks Manufacturing of JIG

Manufacturing of Overhead Assembly13 Weeks

Selection of Sensor3 Weeks

Sensor Calibration

Programming

3 Weeks

Actual

11 Weeks

2 Weeks Testing

Planned

Gantt Chart

References• Jigs and Fixtures design manual by

Hendriksen• Friction and Wear Measurement Techniques

(Niklas Axén, Sture Hogmark, Staffan Jacobson)

• INTERNAL COMBUSTION ENGINE FUNDAMENTALS by John B.LHeywood

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