This document discusses electronic control of automatic transmissions. It begins by introducing automatic transmissions as complex systems with mechanical, hydraulic, electrical, and computer components. It then describes the main components of automatic transmissions, including planetary gear sets, hydraulic systems, clutches, bands, torque converters, and computer controls. It explains how computer controls use sensors to detect driving conditions and control shift points and firmness. The document outlines some issues that can indicate transmission problems in need of repair.

1. BY
ARAVINDKUMAR B
ELECTRONIC CONTROL OF
AUTOMATIC TRANSMISSION

2. INTRODUCTION
The modern automatic transmission is
by far, the most complicated
mechanical component in today’s
automobile.
Automatic transmissions contain
Mechanical systems, Hydraulic
systems, Electrical systems and
Computer controls, all working
together in perfect harmony which
goes virtually unnoticed until there is
a problem.

3. WHAT IS TRANSMISSION ?
• The transmission is a device that is
connected to the back of the engine
and sends the power from the engine
to the drive wheels
• Purpose of the transmission is to
provide high torque at the time of
starting the engine, hill climbing ,
accelerating and pulling a road.

4. TYPES OF AUTOMATIC
TRANSMISSION
• Rear wheel drive
• Front wheel drive

5. REAR WHEEL DRIVE
• The transmission is usually mounted to the
back of the engine.
• Power flow on this system is simple and
straight forward going from the engine,
through the torque converter, then
through the transmission and drive shaft
until it reaches the final drive where it is
split and sent to the two rear wheels.
• Example of rear wheel – Alpha Romeo
Alfeta in early 70’s

6. REAR WHEEL DRIVE

7. FRONT WHEEL DRIVE
• On a front wheel drive car, the transmission is usually
combined with the final drive to form what is called a
transaxle.
• Transaxle is a device set up in the transmission gear box,
clutch, final drive, combined into a single unit.
. Front-wheel-drive layouts are those in which the front
wheels of the vehicle are driven. The most popular layout
used in cars today is the front-engine, front-wheel drive,
with the engine in front of the front axle, driving the
front wheels.
• This layout is typically chosen for its compact packaging.
• Front axles are connected directly to the transaxle and
provide power to the front wheels.

8. FRONT WHEEL DRIVE

9. To improve conventional automatic transmission in the
following ways.
• Gear changes should be smoother and quieter.
• Improved performance.
• Reduced fuel consumption.
• Reduction of characteristic changes over system life.
• Increased reliability.
Electronic control of automatic Transmission

10. Engine Drive Transmission Systems
•The engine drive train system of the automobile consists
of the engine, transmission, drive shaft, differential, and
driven wheels.
•The transmission is a gear system that adjusts the ratio of
engine speed to wheel speed. It enables the engine to
operate within its optimal performance range regardless of
the vehicle load or speed.
•It provides a gear ratio between the engine speed and
vehicle speed such that the engine provides adequate
power to drive the vehicle at any speed.

11. •To accomplish this with a manual transmission, the
driver selects the correct gear ratio from a set of possible
gear ratios.
•An automatic transmission selects this gear ratio by
means of an automatic control system.
•Properly used manual transmission has efficiency
advantages over an automatic transmission, but the
automatic transmission is the most commonly used
transmission for passenger automobiles
Engine Drive Transmission Systems

12. Automatic Transmission
•Automatic transmissions is controlled by a hydraulic and
pneumatic system, but the industry is moving toward electronic
controls.
• The control system must determine the correct gear ratio by
sensing the driver-selected command, accelerator pedal position,
and engine load.
•The proper gear ratio is actually computed in the electronic
transmission control system. The electronic transmission control
can optimize transmission control.
• However, since the engine and transmission function together as
a power-producing unit, it is sensible to control both components
in a single electronic controller.

13. Electronic control of automatic Transmission

14. TRANSMISSION COMPONENTS
• Planetary Gear Sets
• Hydraulic System
Oil Pump
Valve Body
Clutches
 Band
• Seals and Gaskets
• Torque Converter
• Governor
• Computer Controls

15. PLANETARY GEAR SETS
A gear set in which all of the gears
are in one plane, grouped around each
other like the planets around the sun.
The central gear is called the "sun
gear". In mesh with it is a circular
grouping of gears, called "planet
gears", mounted on a rotating carrier.
The planet gears also engage teeth on
the inner periphery of the "ring gear".
By holding any one of the three gear
elements motionless, different ratios
can be produced between the other
two. Planetary gear sets are common in
automatic transmissions.

16. SIDE VIEW

17. CLUTCH PACKS
A clutch is a mechanical
device which provides
for the transmission of
power (and therefore
usually motion) from one
component (the driving
member) to another (the
driven member).
the simplest
application clutches
are employed in
devices which have two
rotating shafts.

18. BANDS
A band is a steel strap
with friction material
bonded to the inside
surface.
One end of the band is
anchored against the
transmission case while
the other end is
connected to a servo.
A flexible metal ring fits around the outside of
the clutch housing. It tightens to engage the
gears, and loosens to release them.

20. TORQUE CONVERTER
A torque converter is
a fluid coupling that
is used to transfer
rotating power from
a prime mover, such
as an
internal combustion en
or electric motor, to
a rotating driven
load.

21. HYDRAULIC SYSTEM
• The Hydraulic system is a complex
maze of passages and tubes that
sends transmission fluid under
pressure to all parts of the
transmission and torque converter
• It works with some components.
 Oil Pump
 Valve Body

22. COMPUTER CONTROLS
The computer uses sensors on the
engine and transmission to detect such
things as throttle position, vehicle
speed, engine speed, engine load, brake
pedal position, etc. to control exact
shift points as well as how soft or firm
the shift should be. Once the
computer receives this information, it
then sends signals to a solenoid pack
inside the transmission

23. NON-COMPUTERIZED
TRANSMISSIONS
• Governor
• Vacuum Modulator
• Throttle Cable
• Seals and Gaskets

24. SPOTTING PROBLEMS BEFORE
THEY GET WORSE
• Watch for leaks or stains under the car.
• Check fluid for color and odor.
• Be sensitive to new noises, vibrations and
shift behavior.

25. TRANSMISSION REPAIRS
• Adjustments and In-Car Repairs
• Reseal job
• Replace accessible parts
• Complete Overhaul
• Replacement unit vs. overhaul existing
unit