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Engine Friction Reduction Through Surface Finish and Coatings
A. Gangopadhyay, D.G. McWatt, R.J. Zdrodowski
Ford Research and Advanced Engineering Dearborn, MI
DEER Conference
October 19, 2012
Contents
• Introduction • System and Subsystem Description • Tribological Conditions • Valvetrain Friction Reduction • Piston Ring Friction Reduction • Summary
System and Subsystem Description
Valvetrain
Ring / Bore contact
Frictional Losses in Engine
Valvetrain19%
Main Bearings
18%
C.R Bearings14%
Accessories12%
Piston Skirt11%
Piston Rings26%
Fric
tion
Coe
ffic
ient
(Viscosity x Speed) / Load
Direct Acting Valvetrain
Piston Rings
Con Rod and Main Bearings
Stribeck Curve
Standard Bucket – 0.10 µm Ra Polished Bucket – 0.04 µm Ra
DLC-Coated Bucket – 0.04 µm Ra Phosphated Bucket – 1.7 µm Ra
Different Bucket Tappet Surfaces in Valvetrain
Cylinder head Torque Meter Flywheel Motor
Coolant line
Motored Friction Measurements
1 piece bucket
Friction Results Mn Phos 5 - 14% improvement
Polished & DLC 17- 25% improvement
Wear Data
Piston Ring / Cylinder Bore Friction • Factors affecting friction
– Piston Ring • Ring coating (Mo-NiCr, PVD,
DLC, nitrided) • Ring tension • Ring design (barrel faced, 2pc vs. 3
pc oil control ring)
– Cylinder bore • Bore finish • Bore coating to replace liners • Bore cylindricity • Honing patterns
Lab bench tests
Single cylinder tests
Engine tests
Testing Sequence
CrN Coating Nitrided layer
Mo-NiCr Coating DLC Coating
Different Piston Ring Coatings Evaluated
Friction Results
Bore Wear
Ring Wear
PVD CrN ring/ PTWA 4130 (Test #30)
0
4
8
12
16
20
0 0.3 0.6 0.9 1.2
Ring width (mm)B
arre
l edg
e (m
icro
ns) 0 hr
20 hr60 hr80 hr100 hr
PVD CrN Ring
NPR DLC-coated ring/ 4130 PTWA(Test #44)
0
4
8
12
16
20
0 0.3 0.6 0.9 1.2
Ring width (mm)
Bar
rel e
dge
(mic
rons
)0 hr20 hr40 hr100 hr
DLC Ring
Moly-filled ring/ CI liner(Test #20)
0
4
8
12
16
20
0 0.3 0.6 0.9 1.2Ring width (mm)
Bar
rel e
dge
(mic
rons
)
40 h60 h80 h100 h
Mo-NiCr Ring
Next Steps • Further opportunities exist with advanced
lubricant technologies • DOE awarded a grant to Ford to explore
polyalkylene glycol base lubricants for engine friction reduction
Summary – Polished buckets showed significant friction
reduction in valvetrain application – DLC coating on piston ring offered some
friction benefit under boundary lubrication condition
– Improved surface finish on piston rings also offered friction reduction
– Thin film coatings showed lower bore wear and coatings appeared to be quite durable
– Opportunities exist for friction reduction with advanced material technologies