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