Efficiency Improvement in Heavy
Duty Axles Confirmed through
Re-design and Testing
Barry James
Chief Technical Officer
27th September 2016
Contents
1. The ETI Lower Drivetrain Parasitic Loss Reduction Project
2. Process for deriving a validated efficiency model
3. Understanding loss contributions  Breakdown of losses
4. Optimising losses by re-design  Gear mesh losses
5. Confirmation testing and drive cycle efficiency improvements
Slide 2
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About the Project
• From 2012, UK’s Energy Technologies Institute funded a project for the reduction in losses in a
HDV axle (Articulated Truck centre axle)
• Targeted outcome (to be confirmed by testing): reduction in losses of 45-55%
New oil
technology
System/component simulation and redesign
60%
Fuel Efficient Bearings
Engineered Surfaces
Project coordination
Efficiency testing
CFD simulation
Slide 3
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About the Project
• Unique offering: A collaborative approach from industry leaders that combine to
provide far more than piecemeal actions alone
Component
Geometry
Lubricant
Definition
Surface
Finish
Manufacturing
Control
Slide 4
Combined
Approach
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Centre axle layout (Romax CONCEPT)
Through shaft to rear axle
(not shown)
Differential with
diff. lock
Half shaft
to wheel hubs
Axle input
(from transmission)
Wheel bearings
transfer
gear set (i=1)
Planetary gear set
Spiral bevel
gear set
Slide 5
Centre fill h=1
(standard)
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Project Overview
2013
Baseline testing
Modelling and Validation
• Understand the current system
• Create validated simulation of the system
that we can modify and optimise
2014
Sensitivity study,
Select optimal solution
2015
2016
• See how the system can be optimised to
gain robust improvements
Detail design and
prototype manufacturing
• Confirm the design, get it made
Confirmation testing
• Test the new design to confirm
improvement
Slide 6
Current status
COMPLETED
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Process for deriving validated efficiency model
No-load tilt rig:
•
•
•
•
Break down of losses by
Speed, temperature and fill level variation
Torque-to-turn measurements
Oil sump and ambient temperature logged
Oil flow investigation using high speed camera
torque/speed/temperature
Loaded rig:
•
•
•
•
•
•
Effect of run-in
Oil temperature variation
Break down of losses for bevel stage+ hubs
Oil sump and ambient temperature logged
input and output torque transducers
temperature sensors in various locations
Simulation and
test data matched
Slide 7
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torque
Break down of losses for selected op. points
(1) High load,
low speed
speed
(3) Low load, high
speed
Slide 8
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Drive cycle efficiency analysis process
Geschwnidgkeit [km/h]
NEFZ
Validated component calculations
150
Efficiency map
100
50
0
0
200
400
600
Zeit [s]
800
1000
Drive cycle simulation
Drive cycle results
Slide 9
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Drive cycle efficiency simulation
• Axle input speed/torque overlaid on calculated efficiency map
Efficiency unloaded dump truck
Efficiency loaded dump truck
Loaded cycle efficiency 90.9%
Unloaded cycle efficiency 86.0%
Slide 10
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Selecting optimisation measures
• Pie chart showing loss contribution over cycle
Loaded dump truck
• Note: all contributors strongly affected by oil
selection
• All contributions relevant for chosen axle
• Converted to fuel efficiency improvement
allows calculation of savings/payback time
Slide 11
Loaded highway truck
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Gear mesh loss reduction
• Efficiency increase by minimising sliding loss factor Hv or friction
coefficient:
𝜂𝑔𝑒𝑎𝑟 = 𝜇𝑚𝑧 ∙ 𝐻𝑉
• Achieved by optimizing the detailed contact geometry in
RomaxDESIGNER
• System effects considered for a robust solution to retain durability and
NVH performance
• Demonstrated before for helical gears, now methodology extended to
bevel and planetary gears
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Low-loss planetary gear design
• Significant loss reduction achieved overcoming constraints of planetary
gears
• Unique capability the subject of a patent
Current Design
New Design
application
• Loss reduction of
15-40% achieved
Slide 13
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R17: FVA 345 Gear Mesh Efficiency Method and Lubricants
• RomaxDESIGNER predicts gear losses due to both gear mesh friction and gear blank
drag
• Lubricant selection offers significant potential to improve drivetrain efficiency by
improving gear mesh efficiency at high loads
• R17 enables improved prediction of the gear mesh losses by accurately predicting
the performance of the chosen lubricant and therefore the resulting gear mesh
friction
• This allows simulation of lubricants of similar viscosity with different
coefficients of friction which are a function of the base oil and additives and can
change depending on the operating regimes
Slide 14
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R17: FVA 345 Gear Mesh Efficiency Method and Lubricants
• R17 includes a new method based on the industry standard test developed by the FZG Institute
(FVA 345), which enables users to measure gear friction for different operating conditions
• This method requires seven new additional lubricant parameters which must be gathered from
a standard test, and then specified in the software
• To assist the user, ten new commonly used example lubricants are provided in the database
(gathered from the public domain, as referenced in the Help file)
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R17: Lubricant effect on efficiency in RomaxDESIGNER
• 2 lubricants with identical viscosities investigated for 2-stage EV gearbox
ISO standard (ISO TR14179-DE) suggests
identical performance
Slide 16
FVA345 method enables differentiation
of lubricants
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Comparison of measured efficiency maps
• Up to 65% power loss reduction confirmed by testing
Slide 17
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Drive cycle efficiency performance of optimised axle
• Good agreement between experiment and simulation found,
load and temperature trend captured
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Menu of Potential Activities
• “Oil designed for machine and machine designed for oil”
o
Comment by Bosch: collaboration of oil and driveline manufacturers
• Design critique and assessment of cost-benefit of changes
• Benchmarking competitor’s oil with respect to driveline
requirements
• Tier-1 suppliers: Benchmarking customer’s oil with respect to
driveline requirements; provide better service
Slide 19
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Summary
• Collaborative project between technology leaders in different areas has given rise to
a unique capability for axle efficiency improvement
• Efficiency optimised on system level using existing RomaxDesigner capability
• Romax committed to develop advanced component loss methods for
implementation in RomaxDesigner
• Predicted improvements in efficiency validated by testing
• Methods and processes applicable to axles and all geared systems
• Project output available in various forms
o
Software, products, test facilities, IP and engineering services
Slide 20
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