ME 205: Tribology & Power Transmission...

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ME 205: Tribology & Power Transmission Elements

ClutchesAsanga Ratnaweera

Dept of Mechanical Engineering

13 December 2006 Asanga Ratnaweera, Department of Mechanical Engineering

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ClutchesCutch is a device to connect driving and driven shafts of a machine, where the driven shaft can be disconnected almost instantaneously from the driving shaft as desired by the operator or driver.

Driving shaft Driven shaft

Clutch

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Classification of clutchesClutches

Jaw Clutches Friction Clutches Hydraulic Clutches

Plate Clutches Cone Clutches Centrifugal Clutches

Single Plate

Multi-plate

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Single plate clutchFlywheel

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Single plate clutch

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Single plate clutchClutch plate

Torsional damper springs

Friction lining

Splined hub

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Single plate clutchPressure plate

Splined hub

Pressure plate

Release levers

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Single plate clutch

Collar bearingPlate clutch

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Recall- Flat Collar BearingsFrictional Torque

The total frictional torque T:Considering uniform pressure (for new bearing)

Considering uniform wear (for old bearing)

⎥⎦

⎤⎢⎣

⎡

−

−= 2

22

1

32

31

32

rrrr

WT µ

[ ]2121 rrWT += µ

13 December 2006 Asanga Ratnaweera, Department of Mechanical Engineering

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The total frictional torque T :Considering uniform pressure (for new bearing)

Considering uniform wear (for old bearing)

Single plate clutch

⎥⎦

⎤⎢⎣

⎡

−−

= 22

21

32

31

322

rrrrWT µ

[ ]21212 rrWT += µ

Cutch plate has two friction surfaces

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13 December 2006 Asanga Ratnaweera, Department of Mechanical Engineering

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Single plate clutchThe total frictional torque T :

R – mean radiusn– number of friction surfaces

For uniform pressure (for new clutches)

For uniform wear (for old clutches)

WRnT µ=

[ ]2

21 rrR +=

⎥⎦

⎤⎢⎣

⎡

−−

= 22

21

32

31

32

rrrrR

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Multi-plate clutch

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Multi-plate clutch

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Multi-plate clutchThe total frictional torque T :

R – mean radiusn– number of friction surfacesn = n1+ n2-1where;n1 – number of discs on the driving shaft n2 – number of discs on the driven shaft

For uniform pressure (for new clutches)

For uniform wear (for old clutches)

WRnT µ=

[ ]2

21 rrR +=

⎥⎦

⎤⎢⎣

⎡

−−

= 22

21

32

31

32

rrrrR

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Cone clutch

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Comparison: Single plate clutch

Cone clutchPlate clutch

W and p are normal to the friction surface dl =drcosecα and pn are normal to the friction surface

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Cone clutchThe total frictional torque T :

R – mean radius

For uniform pressure (for new clutches)

For uniform wear (for old clutches)

WRT µ=

[ ] αecrrR cos2

21 +=

αecrrrrR cos

32

22

21

32

31 ⎥

⎦

⎤⎢⎣

⎡

−−

=

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Cone clutchEngagement

Axial force required for engaging the clutch

For free disengagement

αµ cosne WWW +=

)cos(sin αµα += ne WW

)cos(sin αµα −= ne WW

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Centrifugal clutch

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Centrifugal clutch

RnPPT sc )( −= µ2ωmrPc =2

1ωmrPs =

m – mass of each shoen – number of shoesr - Distance to the centre of gravity of the shoe from the centre of the spiderR – inside radius of pulley rimω – angular speed of the pulley in rad/sω1 – angular speed at the beginning of the engagementµ- coefficient of friction

The total frictional torque