Viscosity Modifiersfor Next Generation Driveline Fluids

Dr. Hitoshi HamaguchiDr. Michael Müller Dr. Christoph WincierzDr. Thorsten BartelsEvonik RohMax Additives

Content

Background

Effect of dPAMA on EHL film formation, friction

and wear

Effect of dPAMA on gear efficiency

Effect of dPAMA on anti-fatigue performance

Conclusions

Transmission – Hardware and Lubricant Technology is Changing Rapidly

Socio-economic and environmental perspective Automobile consumer perspective

•Global warming•Decreasing resources of fossil fuels•Dependency on crude oil deposits

•Driving comfort•Adaptable transmission•Long drain intervals – Fill for life•Reduced operating and service cost

Significantly improvedfuel economyHardware Lubricant

Quantum leap in new transmission technologies

7- and 8-speed AT New generation of CVTs DCT

New transmissions need a new generation of lubricants

Low vis ATF/MTF/CVTF/DCTF

Increased wear and fatigue

Lubricants with boost in wear + pitting

protection

High VI

Low KV40/KV20

Improved fuel economy in city

cycle driving

Highfrictiondurabilityover thelifetime

CO2 emission reduction

Effect of different Viscosity Index Improvers on V-T behavior

logl

og V

isco

sity

logT

base oil

Lower viscosity = reduced internal friction= better energy efficiency

PAMAs allow to formulate to very high VISame KV 100 but much lower viscosities at lower temperaturesYes, PAMAs show some shear thinning at high shear rates But: High shear rates = high entrainment speeds = thick hydrodynamic lubricant films

Measures the lubricant film thickness formed between a rolling steel ball and a silica-coated glass disc, as a function of rolling speed, down to < 2 nm

White Light

--Glass Disc --Thin Cr Layer SiO2 Spacer

Layer Lubricant

Lubricant Film

Specifically designed PAMAs can form thick boundary films in the lubricated contact

Ultrathin film interferometryto measure boundary film formation in situ and in contact

Thick boundary film = lower friction at low speed= better energy efficiency= better wear performance

Dispersant PAMAs: Effect of polymer architecture on film thickness

Polymers with functional groups clustered in a block gave clear thick and considerably viscous boundary films Polymer is adsorbed at the metal surface – boundary film contains higher polymer concentration than bulk fluid Boundary film is stable and survives high pressure rolling- sliding contacts

1

10

100

1000

0.001 0.01 0.1 1 10 Speed [m/s]

Film

Thi

ckne

ss [n

m]

dPAMA O, statdPAMA O, non-stat.dPAMA N1, statdPAMA N1, non-stat.

At slow speed

At high speed

In correlation with film thickness results, non-statistically distributed block copolymers gave a very large reduction in friction at low speed

0.000

0.040

0.080

0.120

0.001 0.01 0.1 1 10

Mean rolling speed [m/s]

Fric

tion

coef

ficie

nt

dPAMA O, stat.

dPAMA O, non-stat.

dPAMA N1, stat.

dPAMA N1, non-stat.

Dispersant PAMAs: Effect of polymer architecture on friction

Even in the presence of a full gear oil package the dispersant PAMA shows boundary film formation and leads to significantly lower friction at low speed

Dispersant PAMAs: Effect in a fully formulated 75W90 gear oil

Formulation basedon group 3 oil.Package contains:DispersantS-based EP additiveAntioxidant, friction modifierVII: PAO 100 ordispersant PAMA

0,00

0,02

0,04

0,06

0,08

0,10

0,12

0,14

1 10 100 1000 10000

Entraiment speed (mm/s)

Fri

ctio

n C

oef

fici

ent

75W90 + PAO 100 75W90 + dPAMA N1

MTM/ICP Wear Test Results for different PAMAs in oil

Block f-PAMAs completely prevent wear under the MTM/ICP conditionsStat f-PAMAs are also quite effectiveNon-functionalized PAMA reduces wear significantly. After an increase over the first hour wear comes to a haltPIB has no marked influence on wear. In its presence wear increases

linearly with time

0

5

10

15

20

25

30

35

40

45

0 1 2 3 4 5

Time (hour)

Iro

n C

on

c (p

pm

)

Reference oilNon-func PAMA f-PAMA (block)f-PAMA (stat)PIB

FZG Efficiency Test Method to measure Lubricant Efficiency

DIN 51354/5, VW PV 1456

Volkswagen Polo gear set

0, 135, and 302 Nm

1600 rpm

T = 20, 44, and 90 °C

Measures the lubricant torque transmitting efficiency through two sets of loaded gears

Simulation of the MVEG cycle (5 speed MT)Formulation details:

VII in mineral oil and PAO, commercial DI packageViscosity according to SAE 75W-90

Gear set 2 Gear set 1 TorqueSensor

Drive-motor

Torque AdjustmentFlange

Torsion Flange

Shaft 2

Shaft 1

FZG Efficiency Test Method to measure Lubricant Efficiency

Temperature and Viscosity Effects on FZG Torque Loss

Conditions: 238 Nm applied torque, 2000 rpm

4

5

6

7

8

30 60 90 120 150

Oil Temperature (°C)

To

rqu

e L

oss

(N

m)

SAE 90SAE 75W-90

Torque loss decreases with increasing temperature Model for increased fuel economy with lower in-service viscosity Multi-grade formulation shows expected benefit at lower temperaturesWhy is there also a benefit ≥ 100ºC?

Influence of VII type on gear efficiency

T = 20 °C

0

2

4

6

0 100 200 300

Transferred torque (Nm)

Ab

solu

te in

crea

se o

f ef

fici

ency

vs

SA

E 9

0

SAE 75W-90 (PAMA)

SAE 80W-90 (PIB)

Efficiency gains versus monograde decreases with increasing torque PAMA improves significantly more than PIB

Influence of VII on load-dependant Losses

PAO formulations have lower torque loss than mineral oil PAO formulated with PAMA shows equal losses to straight PAO

Addition of PAMA to mineral oil causes a decrease in load dependent loss. Higher PAMA concentration increases the effect

Addition of PIB increases load dependent torque loss

2.5

3

3.5

4

4.5

0 10 20 30 402.5

3

3.5

4

4.5

0 10 20 30 40

Mineral Oil (Group I) Formulations PAO Formulations

Viscosity in Kinematic mm2/sKinematic Viscosity in mm2/s

Straight PAO PAO + PAMA PAO + PIB ▲

Straight Mineral Oil SN 150 + PAMA SN 150 + PIB▲ SN 90 + PAMA SN 500 + PIB + SN 500 + PAMA T

orq

ue L

oss in

Nm

Torq

ue L

oss in

Nm

Conditions: 90ºC, 302 Nm applied torque

Efficiency of multigrade MTF:Truck on Roller Dynamometer

Source: ZF

Heavy truck field test revealed 0.5 to 5 % difference in fuel consumption between SAE 90 and SAE 75W-90 depending on topography and temperature.

ZF multigrade fluid SAE 30

KV 100 / cSt 9.0 11.5

KV 30 / cSt 84 170

FIGE cycle (European stationary cycle for HDD), fuel savingsUrban traffic: 2.6 – 3.3 %Suburban traffic: 1,1 – 1,2 %Motorway: 0 % (direct drive)Total Savings 0.7 – 1 %

Source: RohMax

Pitting – an increasing problem withlow viscosity fuel efficient lubricants

Strict CO2 emission requirements

Extreme reductions of fuel consumption Lower viscosity of automotive lubricants required Lower viscosity leads to increased wear and fatigueOptimized lubricant formulations have to compensate for thatRohMax Solution: Tailor-made film forming VII or booster which improves anti-fatigue performance

Potential areas of application:ATF, CVT, DCT, MTF, rear axle, transfer caseEngine oils

Pitting = a fatigue failure occurring at metal surfaces as a consequence of load alternationTarget = no pitting over the lifetime of the equipment = long fatigue life = good anti-fatigue performance

Pitting

Boundary film reduces surface stress peaks at asperities

which are responsible for micro crack formation

leading to pitting

rota

tio

ns

to d

amag

e

Film Forming PAMAs increase fatigue life: 4 ball screening test

conventional PAMA

0

40.000

80.000

120.000

160.000

200.000

new film former 1

new film former 2

RohMax Test ConditionsLoad 4 800 NSpeed 4 000 rpmTemperature 120 °Cp Hertz-max 7.67 GPa

148,000150,000

105,000

Example: 75W MTF oil

Film Forming PAMAs increase fatigue life: FE8 bearing pitting test

Test ConditionsAccording to VW specificationLoad 60 kN Speed 500 rpm / 750 rpmTemperature 120 °Cp Hertz-max 1.45 GPa

Test bearings

0

500

1000

1500

2000

2500

3000

3500

MTF B(0-050)

MTF B(lmw 3,0% H12 graft)

MTF B(7,5% F105 block)conventional

PAMAnew film former 1

new film former 2

2,000 h

480 h

150 h

ho

urs

to

dam

age

Example: 75W MTF oil

Conclusions

Fuel economy in automotive transportation is important today and will be more important in the future.

New transmission hardware requires new generation of fluid technologies

Maximum fuel economy requires improvements in both engine and transmission lubricants, and will drive a shift to lower viscosity lubricants.

Lower viscosity lubricants can adversely affect wear and fatigue life if adequate lubricant film thickness is not maintained.

Tailor-made PAMA viscosity Index improvers simultaneously enable: Reduction of base oil viscosity Reduction of lubricant viscosity at lower temperatures

through higher VI Improved fuel economy

Increase in lubricant film thickness Improved wear and fatigue life