1

Development of 3-D simulation for power

transmitting analysis of CVT driven by dry

hybrid V-belt

Development of 3-D simulation for power

transmitting analysis of CVT driven by dry

hybrid V-belt

Masahide FUJITA Hisayasu MURAKAMI Power Train Research and Development DivisionDaihatsu Motor CO., LTD.

Shigeki OKUNO Mitsuhiko TAKAHASHI Power Transmission Technical Research Center

Bando Chemical Industries, LTD

International Continuously Variable and Hybrid Transmission Congress

September 23-25, 2004

San Francisco, CA

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BackgroundNew CVT3D-simulationOutcomes

Transmitting efficiencyDynamic strain on the belt

Conclusions

ContentsContents

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Main products of Daihatsu: Small-sized Cars

BackgroundBackground

　　　　　 1L 　　　　　　 2L

Application

Metal pushing V-belt

Engine displacement

Excessive quality

Commercialized CVT

New CVT

Higher efficiency

Dry hybrid V-belt

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Blocks (Resin coated aluminum alloy)

Tension bands

Aramid cord Rubber

New CVT with Dry Hybrid V-beltNew CVT with Dry Hybrid V-belt

Advantage:Air coolingNo lubricant

=Higher efficiency

High torque capacity with improved wider belt=Increased belt mass / inertia

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MeritIncrease contact angle

Torque capacity rise

Belt tension controlBetter efficiency

Driving Pulley

Driven Pulley

Tension Pulley

DemeritReverse bending force

Less durability

New CVT systemNew CVT system

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Driving Pulley

Driven Pulley

　3800rpm 30m/s

3-D dynamic simulation3-D dynamic simulation

Belt movement in high speed:

Dynamic measurements is impossible 3-D dynamic FEA is needed

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Required features:Precise inertia force calculationAdvanced contact searchDynamic belt behavior visualization (stress & others)

Explicit FEM codeESI Software's PAM-MEDYSA

(MEchanical DYnamic Stress Analysis)

Selection of FEM codeSelection of FEM code

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Building the model as it isCord anisotropyContacts defined between block & tension band

BlockRubber

Resin

Upperbeam

Lowerbeam Cord

Tension band

Aluminum

Modeling of dry hybrid V-beltModeling of dry hybrid V-belt

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All parts: Defined as elasticComponents of pulley shaft

Sliding interface taking account of shaft clearance

Fixed pulleyMovable pulley

Fixed pulley shaftw/ clearance

Resin bush

Slide keys

Modeling of CVT pulleysModeling of CVT pulleys

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1. Initial state (Belt: Tension free)

2. Move driving pulley (apply tension to the belt)

3. Rotate driving pulleyApply absorbing torque

Driving pulley Driven pulley

Calculation proceduresCalculation procedures

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Calculation procedures: movieCalculation procedures: movie

12Belt velocity (m/s)

Effi

cie

ncy

(%)

Transmitting efficiencyAt high speed running: lower efficiency Difference (simulation/experiment): 2%

All Parts: elastic

Calculated

Measured

949596979899

100

0 10 20 30 40

2%

Ratio ： High (0.407) Input torque ： 80Nm

Outcome on initial modelOutcome on initial model

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949596979899

100

0 10 20 30 40

Belt velocity (m/s)

Effi

cien

cy (%

) Calculated

Measured

Ratio ： High (0.407) Input torque ： 80Nm

Matching of simulation with measurement Solutions:

Take account of friction loss at pulley shaft Increase friction loss between belt and pulleys

Fixed pulley

Movable pulley

Pulley shaftw/ clearance Resin bush

Slide keys

Outcome from improved modelOutcome from improved model

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Clearance between tension band and block

From heat aging

Decrease transmitting efficiency

Belt temperature rise

At final period of belt lifespan:

Permanent deformation of tension bandPermanent deformation of tension band

=

15

90

92

94

96

98

100

0 0.1 0.2 0.3

Clearance (mm)

Effi

cie

ncy

(%

)

Vehicle speed 60Km/h

123Km/h

148Km/h

173Km/h

with belt speed 30m/s

with belt speed 35m/s

Vehicle speed 60Km/h

Effect of permanent deformation Effect of permanent deformation

Calculation result of clearance vs. transmitting efficiency

Final period of lifespan

1.45kw power loss +18 %1.72kw

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At high speed rangeIncrease clearance

Decrease efficiency

Efficiency lowed within 1%Power loss +18%

Belt temperature rise

Effect of permanent deformation Effect of permanent deformation

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At the period of lifespanCrack at lower side of tension bands 　

Dynamic FEACalculate lower side strain

at higher belt speed

crack

Dynamic strain analysisDynamic strain analysis

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Period of contact with tension Pulley

Str

ain Bending

Strain

Strain Peak in dynamic behavior

0

Belt speed: 35m/s 　　　 9.7m/s

Strain peak at tension pulleyStrain peak at tension pulley

Ratio:High (0.407) 　　 Low (2.449)

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0

1

2

3

4

5

6

7

8

9

10

11

12

0 5 10 15 20 25 30 35 40

ﾍﾞﾙﾄ速度 (m/s)

下ｺｸ

ﾞ表面

歪み

（%

)

Strain by dynamic behaviorproportional to Belt Speed squared

calculated strain

Strain in dynamic behavior

S=0.00177*V2+7.96

Ten

sio

n b

an

d

str

ain

(%)

Ben

din

g s

train

Strain analysis at tension pulleyStrain analysis at tension pulley

Belt speed(m/s)

20

8

9

10

11

12

13

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1.00E+07 1.00E+08 1.00E+09Number of cycles to crack failure

Maxim

um

str

ain

of

tensi

on b

and (

%)90℃100℃110℃120℃130℃140℃

Belt temperature rise

Belt speed increase

Crack failure S-N curve Crack failure S-N curve

S

trai

n (

%)

Number of cycles to crack

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Based on S-N curve and calculated strainFull agreementFull agreement

Decrease velocity longer belt life

Prediction of belt lifePrediction of belt life

Velocity of belt(m/s)

Belt

life

(hr)

Exp

erim

ent

Cal

cula

ted

Cal

cula

ted

Exp

erim

ent

Belt temperature ： 130deg C

30m/s 35m/s

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Factors to affect transmitting efficiency:Pulley shaft clearancePermanent deformation of tension band

Friction loss = Lower efficiency at high belt speed

Raise belt temperature

Shorten belt life

Dynamic strain at high belt speed Shorten belt life

Keys to successCooling systemLimit the maximum belt speed

ConclusionsConclusions