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 Division
Daihatsu Motor CO., LTD.
Shigeki OKUNO
Mitsuhiko TAKAHASHI
Power Transmission Technical Research Center
Bando Chemical Industries, LTD
1
Contents
Background
New CVT
3D-simulation
Outcomes
Transmitting efficiency
Dynamic strain on the belt
Conclusions
2
Background
Main products of Daihatsu: Small-sized Cars
Application
Commercialized
CVT
New
CVT
Metal pushing V-belt
Excessive quality
Dry hybrid V-belt
1L
2L
Engine displacement
Higher efficiency
3
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
Tension bands
Blocks
(Resin coated aluminum alloy)
Aramid cord
Rubber
4
New CVT system
Demerit
Merit
Increase contact angle
Torque capacity rise
Belt tension control
Reverse bending
force
Less durability
Better efficiency
Tension Pulley
Driven Pulley
Driving Pulley
5
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
6
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)
7
Modeling of dry hybrid V-belt
Building the model as it is
Cord anisotropy
Contacts defined between block & tension band
Resin
Block
Rubber
Upper
beam
Tension band
Lower
beam
Cord
Aluminum
8
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
9
Calculation procedures
1. Initial state (Belt: Tension free)
2. Move driving pulley (apply tension to the
belt)
3. Rotate driving pulley
Apply absorbing torque
Driving pulley
Driven pulley
10
Calculation procedures: movie
11
Outcome on initial model
Transmitting efficiency
At high speed running: lower efficiency
Difference (simulation/experiment): 2%
Calculated
Ratio： High (0.407) Input torque： 80Nm
All Parts: elastic
Efficiency(%)
Measured
100
99
98
97
96
95
94
2%
0
10
20
30
Belt velocity (m/s)
40
12
Outcome from improved model
 Matching of simulation with measurement
 Solutions:
Movable
pulley
Fixed
pulley
Slide
keys
Efficiency (%)
 Take account of friction loss at pulley shaft
 Increase friction loss between belt and pulleys
100
99
98
97
96
95
94
Ratio： High (0.407) Input torque： 80Nm
Calculated
Measured
0
Pulley shaft
w/ clearance
10
20
30
40
Belt velocity (m/s)
Resin bush
13
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
14
Effect of permanent deformation
Efficiency (%)
100
1.45kw
98
power loss +18 %
1.72kw
96
Vehicle speed
Vehicle
60Km/hspeed 60Km/h
94
123Km/h
92
148Km/h with belt speed 30m/s
173Km/h with belt speed 35m/s
90
0
0.1
0.2
Final period
of lifespan
0.3
Clearance (mm)
Calculation result of clearance vs. transmitting efficiency
15
Effect of permanent deformation
At high speed range
Increase clearance
Decrease efficiency
Efficiency lowed within 1%
Power loss +18%
Belt temperature rise
16
Dynamic strain analysis
At the period of lifespan
Crack at lower side of tension bands
Dynamic FEA
Calculate lower side strain
at higher belt speed
crack
17
Strain peak at tension pulley
Strain Peak in dynamic behavior
Strain
Ratio:High (0.407)
Low (2.449)
Bending
Strain
0
Period of contact with tension
Pulley
Belt speed: 35m/s
9.7m/s
18
Strain analysis at tension pulley
Strain by dynamic behavior
proportional to Belt Speed squared
Strain in dynamic behavior
12
11
10
9
8
Bending strain
band strain(%)
Tension
下ｺｸﾞ表面歪み（%)
calculated strain
7
6
S=0.00177*V2+7.96
5
4
3
2
1
0
0
5
10
15
20
ﾍﾞﾙﾄ速度(m/s)
25
Belt speed(m/s)
30
35
40
19
Maximum strain
of tension band (%)
Strain (%)
Crack failure S-N curve
14
Belt temperature rise
90℃
100℃
110℃
120℃
130℃
140℃
13
12
11
10
9
Belt speed increase
8
1.00E+07
1.00E+08
N um ber ofofcycl
es to to
crack
failure
Number
cycles
crack
1.00E+09
20
Prediction of belt life
Based on S-N curve and calculated strain
Full agreement
Decrease velocity  longer belt life
Calculated
Experiment
Calculated
Experiment
Belt life (hr)
Belt temperature ：130deg C
35m/s
30m/s
Velocity of belt(m/s)
21
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
22