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Shaping the Future
Transmission Systems
Transmission Systems
• Transmission Gear Changing (Shifting)
• Automated Manual Transmissions
• Continuously Variable Transmissions
• Infinitely Variable Transmissions
Transmissions – Shift Perception
Transmissions – Shift Times
Transmissions – Shift Time Profile
Long
itudi
nal
Acce
lera
tion
(g)
Time (seconds)
•Oscillation start up during torque re-instatement is caused by combined engine torque modulation and clutch actuation and is strongly affected by the clutch performance model plus knowledge of temperature dependent friction characteristics
Oscillation continuation is due to lack of driveline damping – not apparent on AT systems (due to torque converter)
Rapid rates of torque reinstatement lead to shorter shift times but can result in higher post shift oscillations
Transmissions – Shift Time Profile
•Oscillation start up during torque re-instatement is caused by combined engine torque modulation and clutch actuation and is strongly affected by the clutch performance model plus knowledge of temperature dependent friction characteristics
Oscillation continuation is due to lack of driveline damping – not apparent on AT systems (due to torque converter)
Rapid rates of torque reinstatement lead to shorter shift times but can result in higher post shift oscillations
Transmissions – Shift Time Profile
Time (seconds)
Long
itudi
nal
Acce
lera
tion
(g)
Transmissions – Shift Time Profile
Shift by Wire and Automated Manual Transmissions
Shift by Wire and Automated Manual Transmissions
Second generation systems (AMT);•Twin clutch,•Twin layshaft•Gear pre-selection•Single cone synchros•Hydraulic shift action and clutch control
First generation systems were based on former manual shift systems (SbW);
• Usually single dry clutch systems with hydraulic and electro hydraulic actuations
• Primary applications, small city vehicles (high shift operation)
• Poor torque interrupt effects and poor clutch thermal performance
First Generation AMTAisin Seiki
2nd Generation AMTGetrag Powershift (Ford, Volvo)
> Dual Clutch
> Hydraulic Actuation
> 10% fuel economy benefit (on Auto)
Automated Manual Transmissions
Automated Manual Transmissions – Shift Perception
Unlike the conventional mechanical system the feel of the shift change (the tactile feedback) can be almost exactly defined within the context of the chosen control system, whether that is the a steering wheel paddle system or an artificial shift level
In the case of the shift level it is usual to include either a mechanical H type – so replicating a manual system or adopt the step-up/step-down convention often used on barrel change systems (e.g motorbikes)
The removal of the gear shift cable associated NVH issues is a major advantage of AMT systems from a ‘pleasibility’ standpoint. The driver is very sensitive to all in-cabin noises and vibrations, particularly those low frequency harmonics associated with the powertrain
Variable Transmissions
Variable Transmissions
Continuous change in output to input ratio – NOT discrete ratios
Ability to transmit power throughout during ratio change
CVT (Continuously Variable Transmission)
Has maximum and minimum ratio limits
Two main families of mechanical CVT> Variable pulley drives
> Rolling contact traction drives
IVT (Infinitely Variable Transmission)
Include within the ratio range a condition with zero output speed whilst the input is rotating (geared neutral)
Advantages• No gear shift• Continuous transmission of torque• Control of engine speed independently of vehicle speed• Ability to operate engine at peak power over wider range of vehicle speeds• Ability to operate at most fuel efficient point for required output power
CVT and IVT
Disadvantages• Mechanical efficiency of ‘variator’ and belts• Parasitic efficiency of transmission system and controller• Compromise between fuel economy and torque margin to achieve
driveability
CVT – Variable Pulley
Primary pulleyposition sets ratio
Secondary pressuresets torque level
CVT – Pulley Operation
CVT – Variable Pulley
Audi A6 2.8L Multitronic
CVT – Variable Pulley
• Ratio spread 6,0• Consumption 9% less than 5-
speed-automatic• Engine torque 310 Nm
Audi A6 2.8L Multitronic
CVT – Variable Pulley
4th GEAR
ENGINE SPEED
CTX LOWRATIO
1st GEAR
2nd GEAR
3rd GEAR
5th GEARCTX HIGHRATIO
AB
C G
J
H
E
D
F
VE
HIC
LE S
PE
ED
I
CVT – Control; StrategiesVariogram
4th GEAR
ENGINE SPEED
CTX LOW RATIO
1st GEAR
2nd GEAR
3rd GEAR
5th GEAR CTX HIGH RATIO
A B
C G
J
H
E
D
F
VE
HIC
LE S
PE
ED
I
A – engine idle
For light acceleration: B – clutch engagement; C to D – constant engine speed and ratio change with vehicle acceleration; D to E – increased engine speed at constant ratio.
Variogram
CVT – Control; Strategies
4th GEAR
ENGINE SPEED
CTX LOW RATIO
1st GEAR
2nd GEAR
3rd GEAR
5th GEAR CTX HIGH RATIO
A B
C G
J
H
E
D
F
VE
HIC
LE S
PE
ED
I
Kickdown: G- clutch engagement; G to H – engine acceleration to maximum speed; H to F vehicle acceleration with maximum power.
Variogram
CVT – Control; Strategies
• Full toroidal, traction drive variator– Fast dynamic response– Torque controlled
• Split power path with epicyclic summing gear– Reverse, forward and ‘geared
neutral’ operation without start-up device
• Twin regime operation– Wide ratio spread
IVT – Torotrak
1 The input disc(s) Powered by the engine
2 The variator roller(s)which picks up the power and transfers it to…
3 The output disc(s)which transmits the power to the drive shaft
IVT – Torotrak
Clos
ed lo
oppre
ssure
contr
oller
Engin
etor
que
contr
oller
Spark TP
Clos
ed lo
open
gine
spee
dco
ntroll
er
Requ
ired
engin
e torq
ue
Targe
t eng
inesp
eed
Requ
ired
reacti
on to
rque
Flywh
eeel
Inertia
Engin
e
IVT
Servo
Pres
sure
JT
+ ++ +
IVT – Torotrak
Sun Geardriven by the Variator
Planet Gear(supported on a carrier)engine driven
Annulusconnected to the output transmission shaftSun Gear
driven by the Variator
Planet Gear(supported on a carrier)engine driven
Annulusconnected to the output transmission shaft
IVT - Series III Layout
Input
EpicyclicGear Gear
Chain Variator High Regime Clutch
Low Regime Clutch
R2
R1
Rv
R13 R3
Output
2
1
3
Input
EpicyclicGear Gear
Chain Variator High Regime Clutch
Low Regime Clutch
R2
R1
Rv
R13 R3
Output
2
1
3
Power recirculation
Low regime; -6 to +15 mph/1000rpm (including geared neutral)
Input
EpicyclicGear Gear
Chain Variator High Regime Clutch
Low Regime Clutch
R2
R1
Rv
R13 R3
Output
2
1
3
Input
EpicyclicGear Gear
Chain Variator High Regime Clutch
Low Regime Clutch
R2
R1
Rv
R13 R3
Output
2
1
3
IVT - Series III LayoutHigh regime +15 to +74 mph/1000rpm (sync. to overdrive)
IVT – Torotrak
Standard Auto Transmission - Engine Operating Envelope – US Highway
500 1000 1500 2000-50
0
50
100
150
200
250
300
350
30%
00%
10%
10%
10%
30%
10%
10%
20%
10%
30%
20%
10%
30%3
0%
50%
71%
61%
20%
30%
10%
50%
50%
91%
30%
141%
10%
40%
00%
30%
151%
121%
212%
30%
121%
182%
111%
00%
101%
242%
91%
292%
232%
141%
232%
333%
302%
504%
242%
81%
383%
484%
635%
666%
706%
666%
948%
13711%15413%
Eng
ine
Torq
ue (
Nm
)
Engine Speed (rpm)
[Fuel consumed (g) shown in boxes]
Tim
e (s
)
10
20
30
40
50
60
70
80
IVT – Fuel Economy Optimisation
IVT - Engine Operating Envelope – US Highway Cycle
500 1000 1500 2000-50
0
50
100
150
200
250
300
350
20%
10%
00%
00%
30%
10%
10%
20%
71%
20%
30%
30%
91%
60%
30%
20%
222%
60%
81%
71%
101%
101%
81%
10%
151%
10%
272%
565%
232%
10%
434%
1039%
928%
1059%
15213%
13611%
31627%
Eng
ine
Torq
ue (
Nm
)
Engine Speed (rpm)
[Fuel consumed (g) shown in boxes]
Tim
e (s
)
20
40
60
80
100
120
140
160
IVT – Fuel Economy Optimisation
Driveability is key to customer acceptance
Calibration is key to driveability solutions
Integrated approach to total powertrain calibration is required
Question mark regarding long term implementation
CVT - IVT Conclusions
Thank you for listening