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Automatic transmission.ppt

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Automatic transmission with its main components

Published in: Automotive

Automatic transmission.ppt

  1. 1. What is automaticWhat is automatic transmissiontransmission??  Changes gear ratios automaticallyChanges gear ratios automatically as the vehicle accelerate oras the vehicle accelerate or deacceleratedeaccelerate Freeing the driver from having toFreeing the driver from having to shift gears manuallyshift gears manually So there is no clutch pedal in anSo there is no clutch pedal in an automatic transmission carautomatic transmission car
  2. 2. Gear-shift modeGear-shift mode
  3. 3. automatic transmissionautomatic transmission operationsoperations MostMost A/T have 3 or four forward speed, PARK, NEUTRAL, andA/T have 3 or four forward speed, PARK, NEUTRAL, and REVERSEREVERSE ItIt starts the vehicle in 1starts the vehicle in 1stst gear. Then it shifts to 2gear. Then it shifts to 2ndnd , 3, 3rdrd & 4& 4thth without assistance from driver . This happen automatically aswithout assistance from driver . This happen automatically as vehicle speed increases & the engine load or throttle openingvehicle speed increases & the engine load or throttle opening decreases.decreases. ToTo slow and stop the vehicle the driver only needs to releaseslow and stop the vehicle the driver only needs to release accelerator pedal or apply brake.accelerator pedal or apply brake. TheThe A/T disengages the torque converter clutch & automaticallyA/T disengages the torque converter clutch & automatically to downshifts until 1to downshifts until 1stst gear and when the vehicle stops.gear and when the vehicle stops.
  4. 4. The main componenTsThe main componenTs Planetary gear setsPlanetary gear sets that provide the various forwardthat provide the various forward gear ratios as well as reversegear ratios as well as reverse Torque converterTorque converter which acts like a clutch to transmitwhich acts like a clutch to transmit torque while the engine is still runningtorque while the engine is still running Hydraulic systemHydraulic system which uses a special transmissionwhich uses a special transmission fluid sent under pressure by an Oil pump to controlfluid sent under pressure by an Oil pump to control thethe ClutchesClutches and theand the planetary gear setsplanetary gear sets GovernorGovernor andand ModulatorModulator oror Throttle valveThrottle valve thatthat monitor speed and throttle position in order tomonitor speed and throttle position in order to determine when to shiftdetermine when to shift
  5. 5. planeTary gear seT •In Neutral, Motion of input shaft turns the Planet gears against the sun gear, it will just spin free and have no effect on the output shaft •In Gear Clutch pack , in this case, lock the output shaft with the sun gear forcing both to turn at the same speed place the unit in.
  6. 6. Torque converTerTorque converTer -- principleprinciple• Large nut shaped device that is mounted between the engine and the transmission • It uses oil or transmission fluid to transmit power.
  7. 7. The hyDraulic sysTem • Complex maze of tubes that sends fluid under under pressure to all parts of the transmission and torque converter. • Transmission fluid serves in shift control, general lubrication and transmission cooling so to keeps the transmission at normal operating temperature • OIL PUMP • VALVE BODY • SHIFT VALVES • BANDS
  8. 8. Oil Pump(Gear Pump)Oil Pump(Gear Pump) • Produce all the oil pressure that is required in the transmission • The oil is then send under pressure to the valve body and the rest of the components, as required.
  9. 9. 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.
  10. 10. Shift Valves • Supply hydraulic pressure to the clutches and bands to engage each gear • Determines when to shift from one gear to the next
  11. 11. GOVERNERGOVERNER Connected to the output shaftConnected to the output shaft and regulates hydraulicand regulates hydraulic pressure based on vehiclepressure based on vehicle speedspeed
  12. 12. COMPUTER CONTROLLSCOMPUTER CONTROLLS • Detect such things as throttle position, vehicle speed,Detect such things as throttle position, vehicle speed, engine speed, engine load, etc.engine speed, engine load, etc. • Downshifting automatically when going downhill.Downshifting automatically when going downhill. • Up shift when braking on a slippery surface.Up shift when braking on a slippery surface.
  13. 13. Comparison with manualComparison with manual transmissiontransmission •Smooth OperationSmooth Operation •Ease of controlEase of control •Infinite number of gearing availableInfinite number of gearing available •Minimum power losses during gear shiftingMinimum power losses during gear shifting Higher cost, lower fuel efficiencyHigher cost, lower fuel efficiency Complicated designComplicated design Possibility of oil leakagePossibility of oil leakage
  14. 14. THANK YOUTHANK YOU

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