Automatic gear transmission

Automatic gear transmission

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  AUTOMATIC GEAR TRANSMISSION By : S.PavanKumar Naik
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  CONTENTS • Introduction • Classification •Automatic transmission using planetary gears • Continuously variable transmission • Conclusion • References
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  INTRODUCTION • Device whichchanges 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 planetarygears Continuously variable transmission(cvt)
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  AUTOMATIC TRANSMISSIONS USING PLANETARYGEARS Components : • Planetary Gear System • Torque Converter • Hydraulic System • Governor • Computer Controls
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  HOW PLANETARY GEARSWORK 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 • Takesthe 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 valves Oil 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 • Thebrain 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 • Supplyhydraulic 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 continuoslyvariable 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 • Detectsuch 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 containmechanical systems, hydraulic systems, electrical systems and computer controls, all working together in perfect harmony
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  REFERENCES www.drivetrain.com www.sciencedirect.com www.scribd.co www.youtube.com http://www.gears-gearbox.com/semi- automatic transmission.html Google, Wikipedia. http://auto.howstuffworks.com