AWD Disconnect - Escaping the clutches of the dog...FWD 25 Schaeffler Symposium 2014 Brian Lee PTU disconnect 65 mm The world hates change, yet it is the only thing that has brought

AWD Disconnect -

Escaping the clutches of the dog

Brian Lee

To think outside the box you must be

outside of the box.

” “

Alfreda Doyle Poet

Pickup Car

Schaeffler Symposium 2014 Brian Lee 2

AWD disconnect consensus?

RWD RWD

FWD FWD

Schaeffler Symposium 2014 Brian Lee 3

The good 'ole dog clutch

Why the consensus on a

dog clutch?

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The good 'ole dog clutch

Failure mode Cause Effect

CRACK!

It's only a dog clutch.

What could go wrong…?

Schaeffler Symposium 2014 Brian Lee 5

Wedge clutch disconnect

Schaeffler Symposium 2014 Brian Lee 6

Wedge clutch disconnect

Actuator

Magnet

Armature

Spring

Clutch

Carrier

Wedge Plate

Hub

Brian Lee

Wedge clutch function

Brian Lee

Taper

Connect Disconnect

2mm

Schaeffler Symposium 2014 7

Schaeffler Symposium 2014 Brian Lee 8

Wedge clutch function

Brian Lee

FT

Plate

Hub

Carrier

α

To

μ1

μ2

Schaeffler Symposium 2014 Brian Lee 9

Actuation principle

Input shaft

Output shaft

Carrier

Hub

Switchable

spring

F = -Y

F = X

Electromagnet Plate

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What's a switchable spring?

Forc

e

+

Diaphragm spring characteristic

Deflection

0 _

Clutch engaged

Clutch disengaged

Deflection

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Requirements of the magnet

Forc

e

+

Deflection

_

Disengaged

Engaged

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Magnet design

a

Air gap "a"

Forc

e

0

Required

force

Required

stroke

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Magnet design

Travel

Forc

e

0

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Clutch lockup testing

Motor

Input inertia

1x106 Kg mm2

Output inertia

5x104 Kg mm2

Torque meter

Test Sample

Wedge clutch lockup

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- Input speed

- Output speed

- Torque

Torque spike

Time in sec

Sp

ee

d in

RP

M

To

rqu

e in

Nm

Dog clutch lockup

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- Input speed

- Output speed

- Torque

Time in sec

Sp

ee

d in

RP

M

To

rqu

e in

Nm

Dog clutch lockup

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- Input speed

- Output speed

- Torque

Time in sec

Sp

ee

d in

RP

M

To

rqu

e in

Nm

Schaeffler Symposium 2014 Brian Lee 18

Wedge clutch To

rqu

e s

pik

e in

Nm

Delta speed in RPM

Wedge

ATF

Wedge

75W-90

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Dog clutch To

rqu

e s

pik

e in

Nm

Delta speed in RPM

Dog

ATF & 75W-90

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Wedge vs. dog clutch To

rqu

e s

pik

e in

Nm

Delta speed in RPM

Dog

Wedge

ATF

Wedge

75W-90

25-30% Improvement

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Wedge – high speed lockup S

pe

ed

in

RP

M

Time in sec

- Input speed

- Output speed

- Torque

Schaeffler Symposium 2014 Brian Lee 22

Dog – high speed lockup S

pe

ed

in

RP

M

Time in sec

- Input speed

- Output speed

- Torque

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High speed lockup

Time in sec

Sp

ee

d in

RP

M

- Input speed

- Output speed

- Torque

Dog tooth

clash

Dog tooth

backlash

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PTU disconnect

FWD

Schaeffler Symposium 2014 Brian Lee 25

PTU disconnect

65 mm

The world hates change, yet it is

the only thing that has brought

progress.

” ‟

Charles Kettering

1876-1958