Automatic transmission in Cars

1. A Presentation on Automatic Transmission
BONGAIGAON POLYTECHNIC
DEPARTMENT OF MECHANICAL AUTOMOBILE ENGG.
SUBMITTED TO
ANANTA KUMAR NATH, M.E.
LECTURER (SG)
&
RABINDRA PATHAK, M.E.
LECTURER (SS)
GAURAB DEHINGIA BOP/19/MA/015
NAME ROLL NO
SUBMITTED BY
01
REPORT ON: AUTOMATIC TRANSMISSION
Gaurab Dehingia

2. Introduction
Operation
Clutch packs
&
Bands
& ECU Unit
CVT,DCT,AMT,ECT
Contents of the report
02
AUTOMATIC TRANSMISSION
Automatic
gear shifter
Components
of AT
Comparison between
Automatic & Manual
transmission
CVT/DCT/AMT?
Conclusion
&
Reference
AT using
Planetary gears
Torque
converter
Hydraulic
system
Oil pump,
Valve body
&
Shift valve
Governor
Computer
controls

3. 02
An automatic transmission is a type of transmission or gearbox
that can automatically change the gears while the vehicle is in
motion. Manufacturers also term it as just the Auto or AT, the
self-shifting transmission. It is also known as the ‘n-speed’
automatic, where n is the number of forward-gear ratios. It is a
type of motor vehicle transmission that frees the drivers from
shifting the gears manually or by themselves. In vehicles with
automatic transmission, there is no clutch pedal. The driver can
control the car only through the accelerator and brake.
What is Automatic transmission?
03
Objective: To study about Automatic transmission and its various types

4. 04
Meanings of letters in a Automatic Gear Shifter

5. Operation in Automatic transmission cars
Most A/T have 3 or four forward speed, PARK, NEUTRAL, and REVERSE.
It starts the vehicle in 1 gear. Then it shifts to 2, 3 & 4 without assistance
from driver. This happen automatically as vehicle speed increases & the
engine load or throttle opening decreases.
To slow and stop the vehicle the driver only needs to release accelerator
pedal or apply brake.
The A/T disengages the torque converter clutch & automatically to
downshifts until 1st gear and when the vehicle stops.
To slow and stop the vehicle the driver only needs to release accelerator
pedal or apply brake.
The A/T disengages the torque converter clutch & automatically
downshifts until 1st gear when the vehicle stops.
Slippage in the torque converter allows the engine to idle with the
transmission in gear.
05
REVERSE
PARK NEUTRAL

6. 06
Main components of a Automatic transmission
Planetary gear sets that provide the various forward gear ratios as well as reverse.
Torque converter which acts like a clutch to transmit torque while the engine is still
running.
Hydraulic system which uses a special transmission fluid sent under pressure by an
Oil pump to control the Clutches and the planetary gear sets.
Governor and Modulator or Throttle valve that monitor speed and throttle position in
order to determine when to shift.
Hydraulic system
Planetary gear sets
Torque converter
Modulator
Governor Throttle valve
Planetary Gear Sets
Torque Converter
Hydraulic System
-Oil Pump
-Valve Body
-Clutch packs
-Band
Governor
Computer Controls
_____________________

7. 07
Automatic transmission using Planetary gears
A gear set in which all of the gears are grouped around each
other like planets around the sun gear.
The central gear is called the sun gear. In mesh its is a
circular grouping of gears called planet gears mounted on a
rotating carrier.
By holding any one of the three gear elements motionless,
different ratio can be produced between the other two.
sun gear
planet gears

8. AUTOMATIC TRANSMISSION
Torque Converter
Takes the place of the clutch found on standard
shift vehicle. It uses oil or transmission fluid to
transmit power Torque converter can be divided
into 3 main members:
07
1) Pump/impeller: It is the driving member and rotates with the
engine.
2) Turbine: The impeller vanes pick up fluid in the converter housing
and direct it toward the turbine.
3) Stator: Fluid flow drives the turbine, and the turbine rotates and
turns the transmission input shaft.
Stator
Turbine
Pump/impeller
08

9. AUTOMATIC TRANSMISSION 09
Complex maze of passages and tubes that sends
transmission fid under pressure to all parts of the
transmission and torque converter.
It works with some components:
Oil pump
Valve body
Shift valve

10. 10
Oil pump
­
Automatic transmissions have a neat pump,
called a oil pump. The pump is usually located in
the cover of the transmission. It draws fluid from a
sump in the bottom of the transmission and feeds
it to the hydraulic system. It also feeds the
transmission cooler and the torque converter.

11. 11
Shift valves
Supply hydraulic pressure to the clutches and bands
to engage each gear.
Determine when to shift from one gear to the next.
The 1 to 2 shift valves determines when to shift from
first to second gear.
It is called the brain of the automatic transmission.
Contains a maze of channels and passages that
direct hydraulic fluid to the numerous valves.
These valves activate the appropriate clutch pack
or band servo to smoothly shift to the appropriate
gear for each driving situation.
Valve body
____________________________________________________

12. 12
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
hosing. It tichtends to engage the gears, and loosens to
release them.
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.
__________________________________________________________

13. 13
Governor
The governor is a clever valve that tells the transmission
how fast the car is going. It is connected to the output, so
the faster the car moves, the faster the governor spins.
Inside the governor is a spring-loaded valve that opens in
proportion to how fast the governor is spinning - the
faster the governor spins, the more the valve opens. Fluid
from the pump is fed to the governor through the output
shaft.
The faster the car goes, the more the governor
valve opens and the higher the pressure of the fluid it lets
through.

14. TCU detects such things as throttle position, vehicle speed,
engine speed, engine load etc. to control exact shift points.
It downshifts automatically when going downhill, to
control speed and reduce wear on the brakes. Up shift
when braking on a slippery surface to reduce the braking
torque applied by the engine & inhibit the up shift when
going into a turn on a winding road.
Computer controls
14

15. Cutaway view of a car
ECU unit and sensors
06
08
15

16. CVT or Continuously Variable Transmission has a continuously variable
CVT or Continuously Variable Transmission has a continuously variable
drive ratio (as opposed to conventionally stepped gear ratios) and uses
drive ratio (as opposed to conventionally stepped gear ratios) and uses
belts, pulleys and sensors rather than gears to maintain a steady
belts, pulleys and sensors rather than gears to maintain a steady
acceleration curve with no pauses for gear changes. Because of this, a
acceleration curve with no pauses for gear changes. Because of this, a
CVT can keep the engine in its optimum power range, thereby
CVT can keep the engine in its optimum power range, thereby
increasing efficiency and gas mileage.
increasing efficiency and gas mileage.
Nissan Micra, Maruti Suzuki Baleno CVT, Hyundai Elite i20 CVT, Honda
Nissan Micra, Maruti Suzuki Baleno CVT, Hyundai Elite i20 CVT, Honda
Jazz are some examples of vehicles with CVT transmission cars in
Jazz are some examples of vehicles with CVT transmission cars in
India.
India.
16

17. A dual-clutch transmission (DCT) (sometimes referred to as a twin-
A dual-clutch transmission (DCT) (sometimes referred to as a twin-
clutch transmission) is a type of multi-speed vehicle transmission
clutch transmission) is a type of multi-speed vehicle transmission
system, that uses two separate clutches for odd and even gear sets.
system, that uses two separate clutches for odd and even gear sets.
The design is often similar to two separate manual transmissions with
The design is often similar to two separate manual transmissions with
their respective clutches contained within one housing, and working as
their respective clutches contained within one housing, and working as
one unit. In car and truck applications, the DCT functions as an
one unit. In car and truck applications, the DCT functions as an
automatic transmission, requiring no driver input to change gears.
automatic transmission, requiring no driver input to change gears.
DCT transmissions have been used on vehicles sold by
DCT transmissions have been used on vehicles sold by
Volkswagen, Audi, SEAT, Skoda, and Bugatti, mostly marketed using
Volkswagen, Audi, SEAT, Skoda, and Bugatti, mostly marketed using
the term Direct-Shift Gearbox.
the term Direct-Shift Gearbox.
17

18. Automated Manual Transmission or AMT, is also known as Semi-
Automated Manual Transmission or AMT, is also known as Semi-
Automatic Transmission (SAT) or Clutchless Manual Transmission
Automatic Transmission (SAT) or Clutchless Manual Transmission
(CMT). Like a manual transmission, an automated manual also employs
(CMT). Like a manual transmission, an automated manual also employs
a mechanical clutch; however, the action of the clutch is not controlled
a mechanical clutch; however, the action of the clutch is not controlled
by the driver via the clutch pedal but rather is automated using
by the driver via the clutch pedal but rather is automated using
electronic, pneumatic or hydraulic controls. Sometimes referred to as a
electronic, pneumatic or hydraulic controls. Sometimes referred to as a
"Direct Shift Gearbox" ("DSG") or a "Sequential Manual Gearbox"
"Direct Shift Gearbox" ("DSG") or a "Sequential Manual Gearbox"
("SMG"), this transmission allows for either fully automatic forward
("SMG"), this transmission allows for either fully automatic forward
gear shifts or manual shifts through the gear selector or through
gear shifts or manual shifts through the gear selector or through
buttons or paddles on the steering wheel.
buttons or paddles on the steering wheel.
18

19. 19
Electronically Controlled Transmissions
Downshift automatically when going downhill to control
speed and reduce wear on the brakes
Upshift when braking on a slippery surface to reduce the
braking torque applied by the engine
Inhibit the upshift when going into a turn on a winding road
Electronically Controlled transmissions can do things like:

20. CVT / DCT / AMT
What should you choose?
If you wanna go for efficiency choose CVT as its more efficient. With almost no delay in gear shift and less moving parts
with almost no downtime, it has better efficiency than the other two systems and is a good choice some people might not
like it as they require the car giving an output while they are driving to fully enjoy the experience. But if you use cars to get
from point A to point B consider CVT.
If you want the feel of gears changing and getting an output from the car and quick acceleration DCT is better than the
rest. It has decent efficiency on its own but compared to CVT it lacks behind.
AMT is a good choice and is easily available as more of the entry-level cars have it and is cheaper compared to DCT and
CVT. Not as smooth as CVT and as fast as DCT it still has its uses.
Every transmission has its own advantages and disadvantages. I hope I was able to help you understand how all of these
works so you can make a better and informed decision.
20
AMT
CVT DCT
DCT
DCT
CVT
CVT
CVT
CVT

21. 14
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_________________
/gaurabdehingia
Comparison of Automatic & Manual transmission
____________________________________
21

22. 22
AUTOMATIC TRANSMISSION
**Lamborghini Urus steering wheel with paddle-shifters

23. slideshare.com/saffrony09/automatic-transmission-45617433?qid=1742ed2a-
88f6-442f-a9c4-297317b25ec2&v=&b=&from_search=4
Automobile Engineering by R.B. Gupta
carbiketech.com/automatic-transmission/
AUTOMATIC TRANSMISSION
https://auto.economictimes.indiatimes.com/amp/news/auto-components/all-
you-need-to-know-about-the-automatic-transmission/
https://gomechanic.in/blog/dct-cvt-amt-automatic-car-transmission/
%3famp
23

24. Scan the QR for webpage slideshow
gaurab.dehingia@gmail.com
7002352953 /gaurabdehingia
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25. This
is
presented
by
Name: Gaurab Dehingia
Roll no: BOP/19/MA/015
Branch: Mechanical Automobile Engineering
Term: 5th Semester
Year: 2022
No. of pages = 25
No. of pages = 25
/gaurabdehingia