Principle and operation of Epi Cyclic gear box

Automatic Transmission:

• In automatic transmission, which is employed in modern cars, even the gears are changed 

  automatically by a control mechanism which is activated by the accelerator pedal only

Automatic transmission consists of:

• Clutch 

• Torque converter 

• Epi cyclic gear box

Automatic transmission operator basically by controlling

• Vehicle speed and engine load

 

Introduction:

 

• In ordinary gearing the axis of various gears is fixed and the motion is simply rotation about

  their own axis

• In the Epi - cyclic gearing system at least one gear not only rotates about its own axis but

  also rotates about some other axis

• In this type of gear box no sliding dog clutches are used for engaging 

• Different gear speeds are obtained by using brakes on the gear drums

Epi-cyclic Gear Box:

• A simple gear set has a sungear about which planets turn round 

• Planet gears are carried by a carrier and a shaft and also in mesh initially with a ring gear

• Different torque ratios / speed ratios  are obtained by making any one of the parts sungear,

  planet gears and the ring gear stationary

• By locking two parts with each other a direct gear is obtained

Various gear ratios: 

• Forward very slow 

• Forward slow 

• Forward fast 

• Forward very fast 

• Reverse slow 

• Reverse fast

Advantages:

• As we are using planetary gears no dog clutches are required 

• It is more compact, as planetary gear is rotating within ring gear 

• The band brakes and multiple clutches are having small dimensions, hence space required

  is less   

• The load is distributed over several gear wheels 

• Due to this reason a greater area of gear tooth contact can be used