AUTOMATIC AUTOMATIC TRANSMISSIONTRANSMISSION

Presented By, Guided By,Presented By, Guided By, Muhammed RiyasMuhammed Riyas Gopinathan.VGopinathan.V SS77MMBB Asst:ProfAsst:Prof NO:103NO:103 Dept of Mechanical Dept of Mechanical EnggEngg

IntroductionIntroduction

• Device which changes gear ratios automaticallyDevice which changes gear ratios automatically• Deliver maximum efficiency Deliver maximum efficiency • Difference between automatic and manual Difference between automatic and manual

transmissiontransmission• Easier to drive because they do not have a clutch Easier to drive because they do not have a clutch

pedal or gearshift leverpedal or gearshift lever• There are two type of automatic transmissionsThere are two type of automatic transmissions

CLASSIFICATIONCLASSIFICATION

AUTOMATIC AUTOMATIC TRANSMISSIONS TRANSMISSIONS USING USING PLANETARY PLANETARY GEARSGEARS

CONTINUOUSLY VARIABLE CONTINUOUSLY VARIABLE TRANSMISSION(CVT)TRANSMISSION(CVT)

AUTOMATIC AUTOMATIC TRANSMISSIONS USING TRANSMISSIONS USING PLANETARY GEARSPLANETARY GEARSComponentsComponents

• PLANETARY GEAR PLANETARY GEAR SYSTEMSYSTEM

• TORQUE TORQUE CONVERTERCONVERTER

• HYDRAULIC SYSTEMHYDRAULIC SYSTEM• GOVERNORGOVERNOR• COMPUTER COMPUTER

CONTROLSCONTROLS

1. Sun gear 2. Planet gear 3. Ring gear 4. Planetary carrier

PLANETARY GEAR SYSTEM

PLANETARY GEAR SYSTEM (SIDE VIEW)

HOW PLANETARY GEARS WORK

Input Output Stationary Calculation Gear Ratio

A Sun (S) Planet Carrier (C) Ring (R) 1 + R/S 3.4:1

B Planet Carrier (C) Ring (R) Sun (S) 1 / (1 + S/R) 0.71:1

C Sun (S) Ring (R) Planet Carrier (C) -R/S -2.4:1

Gear Input Output Fixed Gear Ratio

1st 30-tooth sun 72-tooth ring Planet carrier 2.4:1

2nd

30-tooth sun Planet carrier 36-tooth sun 2.2:1

Planet carrier 72-tooth ring 36-tooth sun 0.67:1

Total 2nd 1.47:1

3rd 30- and 36-tooth suns 72-tooth ring 1.0:1

OD Planet carrier 72-tooth ring 36-tooth sun 0.67:1

Reverse 36-tooth sun 72-tooth ring Planet carrier -2.0:1

•Power transfer can only take place when one of the members is held at rest or if two of the members are locked.

TORQUE CONVERTOR• takes the place of the clutch found on standard shift vehicles • large doughnut shaped device that is mounted between the engine and the transmission • it uses oil or transmission fluid to transmit power• three internal elements that work together to transmit power to the transmission.

TORQUE CONVERTOR

THE HYDRAULIC SYSTEM• complex maze of passages and tubes that sends transmission

fluid under under pressure to all parts of the transmission

and torque converter. • Transmission fluid serves in shift control, general

lubrication and transmission cooling.• Keeps the transmission at normal operating

temperature

• OIL PUMP• VALVE BODY• SHIFT VALVES• BANDS

Gear pumpGear pumpOil PumpOil Pump

• Produce all the oil pressure that is required in the transmission

• The oil is then sent, under pressure to the pressure regulator, the valve body and the rest of the components, as required.

Valve BodyValve Body

• 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.

Shift Valves

• Supply hydraulic pressure to

the clutches and bands to engage each gear• Determines when to shift

from one gear to the next• The 1 to 2 shift valves

determines when to shift from first to second gear.

BandBand• A band is a steel strap with friction material bonded to the inside surface.

GOVERNERGOVERNER• provides the inputs that tell provides the inputs that tell

the transmission when to the transmission when to shiftshift

• connected to the output connected to the output shaft and regulates shaft and regulates hydraulic pressure based on hydraulic pressure based on vehicle speedvehicle speed

COMPUTER CONTROLLSCOMPUTER CONTROLLS

• Detect such things as throttle position, vehicle Detect such things as throttle position, vehicle speed, engine speed, engine load,etc. to control speed, engine speed, engine load,etc. to control exactexact shift pointsshift points

• Downshift automatically when going downhill, Downshift automatically when going downhill, to control speed and reduce wear on the to control speed and reduce wear on the brakes. brakes.

• Up shift when braking on a slippery surface to Up shift when braking on a slippery surface to reduce the braking torque applied by the reduce the braking torque applied by the engine. engine.

• Inhibit the Up shift when going into a turn on a Inhibit the Up shift when going into a turn on a winding road. winding road.

CONCLUSIONCONCLUSIONAutomatic transmissions contain mechanical systems, hydraulic systems, electrical systems and computer controls, all working together in perfect harmony

THANK YOUTHANK YOU