Sunil sharmasuraj karn prakashsusheel palt.aslamd.thamotharan

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Principles Of Self Aligning And

Methods Of Increasing Range Of Regulation.

Department of manufacturing engineering

ANNAMALAI UNIVERSITY

BATCH’B’

Viii semester

STEPLESS SPEED DRIVES &CONTINUOUSLY VARIABLE

TRANSMISSION (CVT)

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INTRODUCTION A continuously variable transmission

(CVT) is a transmission that can change steplessly through an infinite number of effective gear ratios between maximum and minimum values.

This contrasts with other mechanical transmissions that offer a fixed number of gear ratios.

The flexibility of a CVT allows the driving shaft to maintain a constant angular velocity over a range of output velocities.

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ADVANTAGES This can provide better efficency than other

transmissions by enabling the operation to run at its most efficient revolutions per minute (RPM) for a range of operating speeds.

Alternatively it can be used to maximize the performance of a machine by allowing the machine to turn at the RPM at which it produces peak power. This is typically higher than the RPM that achieves peak efficiency.

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APPLICATIONS Many small tractors for home and garden use

have simple rubber belt CVTs Combine harvesters have CVTs. This allows

the operator to slow or accelerate as needed to accommodate variations in thickness of the crop.

Some drill presses and milling machines contain a pulley-based CVT where the output shaft has a pair of manually-adjustable conical pulley halves through which a wide drive belt from the motor loops.

PRINCIPLES OF SELF ALIGNING

initial pressure produced by the weight of a power disc is very small

1.THE FRAME CONTAINIG 2 GEARS CAN ROTATE FRELY ABOUT 3RD SHAFT.

2.FORCE 'P' IS DEVELOPED BETWEEN THE ROLLER AND DISC AS THE MOTION IS TRANSMITTED TO 3RD

SPINDLE THROUGH FRICTION VARIATOR.

3. AS THE OUTSIDE TORQUE IS INCREASED THERE IS A TENDENCY OF GEAR BOX TO ROTATE ABOUT 3RD

SHAFT.

4. PRESSURE BETWEEN ROLLER AND DISC IS INCREASED AND SO CONSEQUENTLY THE FORCE 'P'.

5.THUS SELF-ALIGNING IS EFFECTED.

Let P= initial friction force produced between disc and roller

STEPLESS REGULATION CAN BE CARRIED OUT BY

ELECTRICAL SYSTEM ELECTRONIC SYSTEM HYDRAULIC SYSTEM MECHANICAL FRICTION DRIVE AND

PRESSURE VARIATOR

ADVANTAGES OF STEPLESS REGULATION SYSTEM:

No loss in speed Can arrange speed adjustment without

stopping machine. It reduces time losses and very useful in

automatic tool Hydraulic drive avoids speed fluctuation

methods of Increasing range of regulation

1.BY USING MANY VARIATORS

Only belt drive and gear drive is used

CHARACTERISTICS

Here we donot use the full possibility of 3 variators.

Too many speeds can be repeated.

The system is not very much used because we donot get many number of speed.

2.COMBINATION OF VARIATORS WITH GEAR BOXES

CHARACTERISTICS Shaft 1st can have one constant speed. Shaft 2nd have a particular range of speeds. About shaft 3rd, three different speeds

reduced by gear ratios corresponding to any point on 2nd staff.

>>DIFFICULTIES

If the initial range is big then the ratio cant be achieved as the gear box has its influence

3.VARIATORS WITH EPICYCLIC MECHANISM:

>DISADVANTAGES

>complicated to manufacture.

>can not be used in high speed.

>low efficiency if high range is produced.

>used only in feed drives.

ACKNOWLEDGEMENT:

>Design of Machine Tools, Basu S.K., and Pal D.K.

>Machine tool Design and Numerical Control, Metha N.K.

>GOOGLE SEARCH ENGINE

THANK YOU