Automatic transmission is a type
of gearbox, especially used in the automobile industry for changing gear
ratios automatically. It does not require manual shifting of gears. The
gearbox has a set of selected gear range.
The system is hydraulically operated and makes use of a torque
converter and a set of planetary gears.
Parts of an Automatic Transmission System
An automatic transmission consists of the following parts :
- Torque Converter : It is a device connecting
engine and transmission. The instrument takes place of a mechanical
clutch, allowing the engine to remain running. A torque converter
that provides a variable amount of torque multiplication at low
engine speeds.
- Planetary Gearbox Set : The bands and clutches
of this gear set are actuated with the help of hydraulic servos
controlled by the valve body, thereby providing two or more gear
ratios.
- Valve Body : The system receives pressurized
fluid from a main pump operated torque converter. The pressure
coming from this pump is regulated and used to run a network of
spring-loaded valves, check balls and servo pistons. The valves make
use of pump pressure and the pressure from a centrifugal controller
on the output side.
Use of Automatic Transmission
- Automobiles
- Forklift trucks
- Lawn mowers
Automatic Transmission 
