automatic gear transmission
TRANSCRIPT
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AUTOMATIC GEAR TRANSMISSION
By :
Rohit.S.Kumar (14MD16)
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CONTENTS
• Introduction• Classification• Automatic transmission using planetary gears • Continuously variable transmission• Conclusion• References
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INTRODUCTION
• Device which changes gear ratios automatically
• Deliver maximum efficiency
• Easier to drive because they do not have a clutch pedal or
gearshift lever
• Automatic transmissions contain mechanical systems, hydraulic
systems, electrical systems and computer controls, all working
together in perfect harmony.
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CLASSIFICATION
Automatic transmissions
using planetary gears
Continuously variable transmission(cvt)
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AUTOMATIC TRANSMISSIONS USING PLANETARY GEARS
Components :
• Planetary Gear System
• Torque Converter
• Hydraulic System
• Governor
• Computer Controls
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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
• A gear set in which all of the gears are grouped around each other like the planets around the sun.
• The central gear is called sun gear. In mesh with it 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 ratios can be produced between the other two. Planetary gear sets are common in automatic transmissions.
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TORQUE CONVERTOR• Takes the place of the clutch found on standard shift
vehicles• It uses oil or transmission fluid to transmit power• Torque converter can be divided into 3 main
members:a. Pump/impeller: It is the driving member and rotates
with the engine. b. Turbine: The impeller vanes pick up fluid in the
converter housing and direct it toward the turbine. c. Stator: Fluid flow drives the turbine, and the turbine
rotates and turns the transmission input shaft.
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TORQUE CONVERTOR
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THE HYDRAULIC SYSTEM
• 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• Shift valvesOil pump: The oil is then sent, under pressure to the pressure
regulator, the valve body and the rest of the components, as required.
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VALVE 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.
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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.
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• A continuosly variable transmission is a transmission which can change steplessly through an infinite number of effective gear ratios between maximum and minimum values.
• CVTs operate smoothly since there are no gear changes which cause sudden jerks .
• There are 25% fewer moving parts to a CVT transmission
Continuously variable transmission
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COMPUTER CONTROLLS
• Detect such things as throttle position, vehicle speed, engine speed, engine load etc. To control exact shift points .
• Downshift 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.
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CONCLUSION
Automatic transmissions contain mechanical systems, hydraulic systems, electrical systems and computer controls, all working together in perfect harmony
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REFERENCESwww.drivetrain.com www.sciencedirect.comwww.scribd.cowww.youtube.comhttp://www.gears-gearbox.com/semi-automatic transmission.html Google , Wikipedia.http://auto.howstuffworks.com
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