Automatic transmissions allow a vehicle to change gears automatically rather than manually. They consist of a torque converter, planetary gear sets, hydraulic system, and clutches that work together. A torque converter transfers power from the engine to the transmission and provides a continuous speed ratio. Planetary gear sets use epicyclic gears to achieve various gear ratios. Hydraulic controls use transmission fluid under pressure to engage clutches and bands and shift gears depending on running conditions. Automatic transmissions make driving easier by shifting gears without driver input.

1. Technical seminar
AUTOMATIC TRANSMISSION
by
karthick s

2. INTRODUCTION
A transmission is a machine in a power transmission system,
which provides controlled application of the power. Often the
term transmission refers simply to the gearbox that
uses gears and gear trains to
provide speed and torque conversions from a rotating power
source to another device.
Often, a transmission has multiple gear ratios (or simply
"gears") with the ability to switch between them as speed
varies. This switching may be done manually (by the operator)
or automatically. Single-ratio transmissions also exist, which
simply change the speed and torque of motor output.

3. Types of transmission
Manual transmission:
In a manual transmission, the gears are shifted manually .usually,
with a stick located on the console and the clutch
Automatic transmission:
In an automatic transmission, the mechanism changes without
any help from the driver .controlled hydro mechanically. Now the
trend is to use electronic control to shift the gears.

4. Automatic transmission

5. Components of automatic transmission
Torque convertor
Planetary gear sets
Hydraulic system
Clutches and bands

6. Torque convertor
Impeller
Turbine
Stator
Torque convertor ,automatically
transfers engine torque to the
automatic transmission input
shaft.
It provides continuous variation
of speed ratio from high to low.

7. Planetary gear sets
• An epicyclic gear train consists of
two gears mounted so that the
center of one gear revolves around
the center of the other. A carrier
connects the centers of the two
gears and rotates to carry one gear,
called the planet gear, around the
other, called the sun gear. The
planet and sun gears mesh so that
their pitch circles roll without slip.
In this simplified case, the sun gear
is fixed and the planetary gear(s)
roll around the sun gear.

8. Working

9. Hydraulic controls
Uses special transmission fluid sent under pressure by an oil pump to control
various clutches and bands modifying the speed of the output depending on the
vehicle's running condition.
The input for the pump is connected to the torque converter housing, so the
pump provides pressure whenever the engine is running and there is enough
transmission fluid
 But the disadvantage is that when the engine is not running, no oil pressure is
available to operate the main components of the transmission, and is thus
impossible to push-start a vehicle equipped with an automatic transmission.

10. Clutches and bands

11. Governor
The governor is connected to
the output shaft and regulates
the hydraulic pressure
depending on the vehicle speed.
The engine load is monitored
either by a throttle cable or a
vacuum modulator

12. Advantages
Automatic transmission does not offer the driver more control of the
vehicle as compare to that of automatic transmission system.
 You aren’t required to constantly monitor what gear you’re in, or if
you need to shift up or down.
Automatic transmission cars is easy to learn.

13. Reference
 Qadeer Ahmed, Mukilan Arasu, Jiyu Zhang and Giorgio
Rizzoni Center for Automotive Research, College of Engineering,
The Ohio State University, Columbus, OH 43212, USA
Yunfeng HuLu Tian Bingzhao Gao¤ Hong Chen
• State Key Laboratory of Automobile Dynamic Simulation,
JilinUniversity, Changchun Jilin 130025 China .Changchun Jilin
130025 China
 Department of Control Science and Engineering, Jilin University,

14. Conclusion
• In this fast working world, people doesn’t matter about cost. they
matter about only easy way to make things faster with out effort.