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Powersplit drives with mechanical variators
for small mobile machines
Prof. Dr.-Ing. G. Jacobs
Dr.-Ing. F. Straßburger
Christian Pelger, M.Sc.
© VDI Wissensforum 2016 – Veranstaltungsunterlagen – nur zum persönlichen Gebrauch
Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
Content
•Motivation
•Industrial applications of mechanical CVTs
•Market potential of tractor-drives with mechanical CVTs
•Mechanical CVT technologies in comparison
•Powersplit drivetrain structures for mech. CVTs
•Powersplit CVT concept for 65 kW tractor application
•Conclusion
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© VDI Wissensforum 2016 – Veranstaltungsunterlagen – nur zum persönlichen Gebrauch
Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
Motivation
Are Mechanical CVTs an
appropriate solution?
•Transmission characteristics?
•Power and torque limits?
•Cost advantages?
Small and medium sized mobile machines
•Compact tractors
•Forklifts
•Courtyard loaders
•Municipal machinery
Demand for efficient, low noise, cost
competitive and comfortable drives
source: manufacturer websites
source: GIF-Esource: JTEKT
source: LUK
3 to 16
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Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
Industrial applications of mechanical CVTs
•CNH Easy-Drive (Boomer 3000)
Engine max. torque: 140 up to 180 Nm
4-wheel drive
Weight: 1800 kg
5 to 11 % increased PTO-Power due to
higher drivetrain efficiency (compared
to hydrostatic drive)
•Carraro/Torotrak VaryT 5 concept
Engine Power: 56 kW
CVT-Technology: 2x full-toroidal variator in back-to-back
arrangement
Driving modes: 0 to 10 kph powersplit / 10 to 50kph direct
Reversing: stepless in powersplit mode
•Oerlikon Graziano
Engine Power: 30 to 37 kW
CVT-Technology: CVT-chain
Driving modes: powersplit with
reversing clutch
Speed range: 0 to 30 kph
source: CNH
source: Carraro
source: Oerlikon Graziano
source: Torotrak
40%
40%
18%
2%
Market share of automotive
transmissions in Japan &
Korea
Automatic
transmissions
CVT
transmissions
Manual
transmissions
Double clutch
transmissions
source: IHS Automotive 2014
4 to 16
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Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
Market potential of tractor-drives with mechanical CVTs
Tractor admissions classified by engine-power
Europe
low power medium power high power
40k
64k
117k
North America
low power
(< 37 kW)
medium power
(37 to 74 kW)
high power
(>75 kW)
100k
56k
39k
source: Market survey by IME
- VDMA Wirtschaftsbericht 2014
- Credit Suisse
- Association of Equipment
Manufacturers
- Agrievolution
0
5.000
10.000
15.000
20.000
25.000
30.000
35.000
40.000
> 147 kW
11 - 147 kW
75 - 110 kW
38 - 74 kW
< 37 kW
source: VDMA
2005 2010 2011 2012 2013 2014
Huge market potential for mechanical CVTs, designed
for small and medium powered tractor applications
Germany
Tractor admissions [-]
5 to 16
© VDI Wissensforum 2016 – Veranstaltungsunterlagen – nur zum persönlichen Gebrauch
Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
Mechanical CVT technologies in comparison
Basic working principles of mechanical CVTs
Chain drives Friction gears
Tin
Tout
i=1i>1 i<1
toroid
cone-ring
Kopp
disc
Tin
Tout
Tin Tout Tin Tout
Tin
Tout
source: Stuffer
6 to 16
© VDI Wissensforum 2016 – Veranstaltungsunterlagen – nur zum persönlichen Gebrauch
Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
Mechanical CVT technologies in comparison
Chain drives
power transfer by pulling
power transfer by pushing
Robustness through clamping
force control systems
1. Constant flow system (torque-
proportional hydraulic throttle)
2. Pressure regulated throttle
3. Pressure regulated throttle +
mechanical torque sensor
η
source: LUK
source: Bosch
source: LUK
F
F
0%
20%
40%
60%
80%
100%
starting
clutch
hydraulic
pump
mechanical
losses
source: Jatco
Gearbox losses [%]
(in US combined test cycle)
7 to 16
© VDI Wissensforum 2016 – Veranstaltungsunterlagen – nur zum persönlichen Gebrauch
Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
Mechanical CVT technologies in comparison
Friction gears
Troroid variator
Back-to-back
configuration
practical
Cone-ring variator
hydraulic pump
efficient electrical
actuation
efficient ball-ramp
torque sensor
+
F
output shaft
output cone
torque-
sensor
high clamping
forces required
adjustment bridge
ring
output cone
input cone
adjustment
frame
source: Ultimate
Transmissoins
roller Input disc
thrust bearing
output disc
High thrust bearing loads
require a hydraulic actuation
source: GIF-E
source: Nissan
8 to 16
© VDI Wissensforum 2016 – Veranstaltungsunterlagen – nur zum persönlichen Gebrauch
Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
Mechanical CVT technologies in comparison
Powersplit drives
to increase efficiency
Powersplit drives to
increase ratio spread
Variator type
Gravimetric power
density (peak power) 3.0 kW / kg ~ 5.7 kW / kg ~ 4.6 kW / kg ~ 5.0 kW / kg
Cost per kilogram 18 €/kg ~ 21 €/kg ~ 21€ / kg ~ 21 €/kg
Max. torque > 2000 Nm 500 Nm 430 Nm 375 Nm
Ratio spread ~ 11 6 4.3 6
Geared-neutral yes no no no
Actuation hydraulic hydraulic hydraulic electrical
System efficiency
(full load) 65 % - 80 % 85% to 93 % 85 % to 93 % 90 % - 95 %
source: Bosch Rexroth
sources:
Naunheimer
Ultimate Transmisions
LUK, Torotrak, GIF-E
NSK, Bosch Rexroth
To fulfill spec:
9 to 16
© VDI Wissensforum 2016 – Veranstaltungsunterlagen – nur zum persönlichen Gebrauch
Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
Powersplit drivetrain structures for mechanical CVTs
Achieving geared neutral with mechanical CVT’s
Output coupled powersplit structures
mech.
variator
engine
planetary gear
variator directly coupled to output
Input coupled powersplit structures
n = 0
n > 0
n > 0
starting only with IVT-variator possible
(e.g. hydraulic variator)
mech.
variator
engine
planetary gear
n > 0 n = 0
n > 0
S
RC
sun
= variator shaft
ring
= engine shaft
carrier
= output
vvar vout
Input coupled powersplit structures are suitable to
realize the start up process with mechanical CVTs
10 to 16
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Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
Powersplit drivetrain structures for mechanical CVTs
Synthesis of powersplit drivetrain structures
tractive force
vehicle speed
power hyperbola
torque limited below 4 km/h
engine
variator
imin imax
nmin nmax
i1
i2
i3i4
i0
Tractive power target
Boundary conditions
Engine speeds
Variator ratio spread, torque and speed limits
Optimizing gear ratios for ideal
variator ratio utilization
Defining torque distribution between variator
path and mechanical path
Defining variator speed
Defining powersplit mode
Scaling torque load on gearbox and driving
speeds
i1
i0
i2/3
i4
Power to speed
characteristic
15 kW 30 kW 45 kW
Vmax(15 kW)
Vmax(30 kW)
Vmax(45 kW)
11 to 16
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Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
10
15
20
25
30
35
40
45
50
010 20 30 40 50 60
cone-ring-variator
chain - variator
toroidal - variator
maximum driving speed in km/h
engine power in kW
Powersplit drivetrain structures for mechanical CVTs
Structures with one driving mode
Boundary conditions for drivetrain optimization
•Driving speed range : 0 km/h to vmax
•Engine speeds: 1800 min-1 (max torque) to
2600 min-1 (max power)
•Average efficiency: ~90 %
chain
variator
30 kW -3-0,55 1.23
-1
-14.8
S
RC
chain
variator
30 kW -3-0,59 -1.64
-1
19.7
S
R
C
chain
variator
30 kW -3-0,59 0.137
-1
-44.4
S
R
C
IC-SRC structure
IC-SCR structure
IC-RSC structure
suitable for low-power applications
Redundant transmission behavior
source: manufacturer websites
12 to 16
© VDI Wissensforum 2016 – Veranstaltungsunterlagen – nur zum persönlichen Gebrauch
Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
Powersplit drivetrain structures for mechanical CVTs
Structures with two driving modes
C1
C2
Coupled planetary
gear mode
Idle planetary gear mode
Structure variants
2nd direct driving
mode practical
Idle power
at startup
Variator speed
defined by engine
Increased torque
load on variator
+=
Highest speed at
maximum variator ratio
Variator slows down
during acceleration
13 to 16
To reduce
gearbox load i4vmax
© VDI Wissensforum 2016 – Veranstaltungsunterlagen – nur zum persönlichen Gebrauch
Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
North America
low power
(< 37 kW)
medium power
(37 to 74 kW)
high power
(>75 kW)
Powersplit drivetrain structures for mechanical CVTs
Structures with two driving modes
40
50
60
70
80
90
20 40 60 80
maximum driving speed in km/h
engine power in kW
relevant driving speeds for tractor applications
Boundary conditions for drivetrain optimization
Driving speed range : 0 km/h to vmax
Engine speeds: 1600 min-1 (max torque) to
2000 min-1 (max power)
Maximum system efficiency: ~90 %
Carraro
chain
– variator
cone
-ring-variator
toroidal
- variator
suitable for mid-power applications
C2
C1
CRV
65 kW -3-0,46 1,3
-0.8
-57
S
RC
65 kW powersplit concept with
electrically actuated cone-ring variator
40 km/h
50 km/h
60 km/h
~ 90 kW
76 kW
64 kW
75 kW
61 kW
51 kW
64 kW
51 kW
<
41 kW
14 to 16
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Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
Powersplit CVT concept for 65 kW tractor application
Fendt – Vario 209 Powersplit cone-ring
Variator technology Hydrostatic drive
~ 60kg
375 Nm cone-ring-
variator with electrical
actuation ~ 55 kg
Variator costs 18 €/kg
1080€
21 €/kg
1155 €
Number of clutches 0 2
Reversing gear No Yes
Number of
additional gears
- 4
Approximate
additional total cost
- ~ 200 €
Approximate full-
load efficiency
80 % to 85 % 84 % to 92 %
source: Fendt
source: GIF-E
At least 5.5% reduced fuel consumption with mechanical CVT concept
~ 0.6 €/h (for 11 l/h fuel consumption)
ROI after ~ 330 h
15 to 16
© VDI Wissensforum 2016 – Veranstaltungsunterlagen – nur zum persönlichen Gebrauch
Powersplit drives with mechanical variators for small mobile machines
Prof. Dr.-Ing. G. Jacobs | 21.06.2016
Conclusion
... are capable to realize the startup process without an external starting element.
… are relevant for low power tractor applications up to 30 kW.
... with two driving modes are relevant for tractor applications up to 90 kW.
… are slightly more cost-intensive then hydrostatic powersplit transmissions.
Return of invest in less then a year realistic
Mechanical CVTs in powersplit transmissions …
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