Planetary Gearset & Simpson

Planetary Gearset

Planetary Gearset

A simple planetary or epicyclic gearset can provide

overdrive,

reverse,

forward reduction,

neutral, and

direct drive ratios.

Planetary Gearset

3 main Components

Sun gear with external gear teeth

Carrier with planetary pinion gears mounted to it

An internally toothed ring gear or annulus

Planetary gear configuration

Maximum forward reduction

Maximum forward reduction

greatest torque,

lowest speed

is produced with the sun gear as input, the ring gear

stationary, and the carrier as the output.

Maximum Overdrive

Maximum overdrive

lowest torque,

greatest speed

is produced with the carrier as input, the ring gear

stationary, and the sun gear as output.

Minimum forward reduction

Minimum forward reduction

good torque

low speed

is produced with the ring gear as input, the sun gear

stationary, and the carrier as the output

Slow Overdrive

Slow overdrive

lower torque

greater speed

is produced with the carrier as input, the sun gear

stationary, and the ring gear as output.

Slow Reverse

Slow reverse

opposite output direction

greatest torque

lowest speed

is produced with the sun gear as input, the planetary

carrier stationary, and the ring gear as output.

Fast Reverse

Fast reverse

opposite output direction

greater torque

low speed

is produced with the ring gear as input, the carrier

stationary, and the sun gear as output.

Direct Drive

Direct Drive

Direct drive is produced if any two gearset

members are locked together.

Neutral Condition

Neutral Condition

With no held or stationary member, there can

be no output. The result is a neutral condition.

Planetary Gearset

An automatic transmission does not require a conventional

flywheel because the weight of the torque converter

provides enough mass to dampen engine vibrations.

Planetary Gearset

Planetary Gearset

Planetary Gearset

Planetary Gearset

SIMPSON GEAR TRAIN

One of the most popular compound planetary design is the

Simpson gear set.

Named for its inventor, Howard Woodworth Simpson

(18921963), an American automotive engineer, the

Simpson gear set consists of two simple planetary gear sets

that share a common sun gear.

This combination is capable of providing three forward

gears, as well as neutral and reverse.

Shift Modes

Shift Modes : P

The engine will only start if the selector is in either the park

or neutral position.

In park, the drive shaft is locked so that the drive wheels

cannot move.

Shift Modes : R

The reverse gear selector position is used to move the

vehicle in reverse.

Reverse usually uses a lower gear ratio than any of the

forward gears.

Shift Modes : N

In the neutral position no torque is being transmitted

through the automatic transmission/transaxle.

Shift Modes : D

For ordinary driving, the driver moves the selector to the

drive position.

The transmission starts out in the lowest gear and

automatically shifts into higher gears as the car picks up

speed.

Shift Modes : 2

The second position is used for slowing the vehicle while

descending long grades.

In this gear selection, the vehicle speed is controlled and

the engine speed is increased to provide engine

compression braking.

This gear selection is used for the gentle grades at a

moderate vehicle speed.

Shift Modes : L

The first (or low) position is used for slowing the vehicle

while descending long grades.

In this gear selection, the vehicle speed is controlled and

the engine speed is increased to provide engine

compression breaking.

This gear selection is used for the steepest grades at the

lowest possible speed.

Clutch Application Chart

Schematic

Schematic D 1

Schematic D 1

Powerflow D 1

Schematic D 2

Schematic D 2

Powerflow D 2

Schematic D 3

Schematic D 3

Powerflow D 3

Powerflow D 3

Schematic R

Powerflow R