Development of 3-D simulation for power transmitting analysis of CVT driven by dry hybrid V-belt

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Development of 3-D simulation for power
transmitting analysis of CVT driven by dry hybrid
V-belt
International Continuously Variable and Hybrid
Transmission Congress September 23-25, 2004 San
Francisco, CA

• 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

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Contents

• Background
• New CVT
• 3D-simulation
• Outcomes
• Transmitting efficiency
• Dynamic strain on the belt
• Conclusions

3
Background

• Main products of Daihatsu Small-sized Cars

Application
New CVT
Commercialized CVT
Metal pushing V-belt
Excessive quality
Dry hybrid V-belt
1L 2L
Higher efficiency
Engine displacement
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New CVT with Dry Hybrid V-belt

• Advantage
• Air cooling
• No lubricant
• Higher efficiency
• High torque capacity with improved wider belt
• Increased belt mass / inertia

Rubber
5
New CVT system

• Merit
• Increase contact angle
• Torque capacity rise
• Belt tension control
• Better efficiency

Tension Pulley
Driven Pulley
Driving Pulley
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3-D dynamic simulation

• Belt movement in high speed
• Dynamic measurements is impossible
• 3-D dynamic FEA is needed

Driven Pulley
Driving Pulley
3800rpm
30m/s
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Selection of FEM code

• Required features
• Precise inertia force calculation
• Advanced contact search
• Dynamic belt behavior visualization (stress
  others)
• Explicit FEM code
• ESI Software's PAM-MEDYSA(MEchanical DYnamic
  Stress Analysis)

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Modeling of dry hybrid V-belt

• Building the model as it is
• Cord anisotropy
• Contacts defined between block tension band

Block
Resin
Rubber
Upperbeam
Tension band
Lowerbeam
Cord
Aluminum
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Modeling of CVT pulleys

• All parts Defined as elastic
• Components of pulley shaft
• Sliding interface taking account of shaft
  clearance

Fixed pulley
Movable pulley
Slide keys
Fixed pulley shaft w/ clearance
Resin bush
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Calculation procedures

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
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Calculation procedures movie
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Outcome on initial model

• Transmitting efficiency
• At high speed running lower efficiency
• Difference (simulation/experiment) 2

Calculated
Ratio High (0.407) Input torque 80Nm
Measured
All Parts elastic
2
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Outcome from improved model

• Matching of simulation with measurement
• Solutions
• Take account of friction loss at pulley shaft
• Increase friction loss between belt and pulleys

Ratio High (0.407) Input torque 80Nm
Calculated
Movable pulley
Measured
Slide keys
Fixed pulley
Pulley shaft w/ clearance
Resin bush
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Permanent deformation of tension band
From heat aging
Clearance between tension band and block

At final period of belt lifespan

• Decrease transmitting efficiency
• Belt temperature rise

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Effect of permanent deformation

Final period of lifespan
Calculation result of clearance vs. transmitting
efficiency
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Effect of permanent deformation

• At high speed range
• Increase clearance
• Decrease efficiency
• Efficiency lowed within 1
• Power loss 18
• Belt temperature rise

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Dynamic strain analysis

• At the period of lifespan
• Crack at lower side of tension bands
• Dynamic FEA
• Calculate lower side strainat higher belt speed

crack
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Strain peak at tension pulley
Strain Peak in dynamic behavior
RatioHigh (0.407) Low (2.449)
Strain
Bending Strain
0
Belt speed 35m/s 9.7m/s
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Strain analysis at tension pulley

• Strain by dynamic behavior
• proportional to Belt Speed squared

Strain in dynamic behavior
calculated strain
Tension band strain()
Bending strain
S0.00177V27.96
Belt speed(m/s)

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Crack failure S-N curve
Belt temperature rise
Strain ()
Belt speed increase
Number of cycles to crack
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Prediction of belt life

• Based on S-N curve and calculated strain
• Full agreement
• Decrease velocity ? longer belt life

Belt temperature 130deg C
Experiment
Calculated
Experiment
Calculated
35m/s
30m/s
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Conclusions

• Factors to affect transmitting efficiency
• Pulley shaft clearance
• Permanent 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 success
• Cooling system
• Limit the maximum belt speed