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Transmission system
- 1. Automotive Transmission By Tejas Sharma BESkilled BEBE Skilled BE SmartSmart
- 2. Transmission System • Functionof transmission: - It is used to transmit engine torque to the driving wheels to drive the vehicle on the road.
- 3. Requirement of TransmissionSystem • To provide for disconnecting the engine from the driving wheels • When engine is running , connect the driving wheels to engine smoothly without shock • Leverage between engine and driving wheels to be varied • Enable the driving wheels to rotate at different speeds. • Provide relative movement between engine and driving wheels
- 4. Transmission System -Layout
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- 6. Clutch Function of clutch •Clutch is used to disengage and engage the engine with rest of the transmission systems. • To disengage while starting the engine and while changing gear ratio. • To engage after starting of the engine and gear shift operation.
- 7. Clutch Requirement of Clutch •Transmit maximum torque of the engine. • Engage gradually to avoid sudden jerks. • Dissipate maximum amount of heat. • Damp the vibrations and noise. • Dynamically balanced. • As small as possible. • Easy to operate.
- 8. Clutch Unit • Flywheelalso acts as a driving member • Pressure plate is connected to clutch cover assembly. • Clutch Cover assembly is bolted to the flywheel. • Clutch springs placed between Pressure plate & Cover plate, press the Pressure plate against the clutch plate. • Thus Clutch plate is squeezed between Flywheel & Pressure plate.
- 9. Classification of Clutch •Cone clutch • Flat Plate clutch - Dry or Wet type clutch - No. of friction plates (Single or Multiple) - Actuation mode (Cable or Hydraulic) - Actuation spring (Helical or Diaphragm) • Centrifugal clutch
- 10. Clutch Engaged &Disengaged • Clutch is always is in engaged state. • It can be disengaged by pressing of Clutch pedal. Disengagement is effected by non - contact of Clutch plate both with Flywheel face & Pressure plate face. • Frictional heat is dissipated by openings present in Clutch housing & Cover
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- 12. Need of GearBox
- 13. Gear Box • Gearbox varies the leverage (speed ratio & hence torque ratio) between the engine & driving wheels. • It is located between Clutch & Propeller shaft. • It is provided with either 4 speed or 5 speed ratios or more depending on design. • Gear ratio is varied by Gear shift lever.
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- 15. Synchronizers • A deviceused to bring two adjacent members to the same speed before allowing the sleeve to engage them. • The two elements are friction clutch and toothed clutch. • Lock the positive engagement until speeds are synchronized . • Establish the positive engagement and power flow. • Synchronizer is splined on the shaft Cone on the gear (blue) fits into cone-shaped area in the collar. • Friction between the cone and collar synchronize the collar & gear. • The outer portion of the collar (sleeve) then slides so that the dogteeth engage the gear.
- 16. How Manual TransmissionWork? • When a driver wants to change from one gear to another in a standard stick-shift car, he first presses down the clutch pedal • This operates a single clutch, which disconnects the engine from the gearbox and interrupts power flow to the transmission • Then the driver uses the stick shift to select a new gear, a process that involves moving a toothed collar from one gear wheel to another gear wheel of a different size • Devices called synchronizers match the gears before they are engaged to prevent grinding • Once the new gear is engaged, the driver releases the clutch pedal, which re-connects the engine to the gearbox and transmits power to the wheels.
- 17. Manual Transmission • Cheapto make • Durable, efficient • Easy to install • Established in marketplace and with manufacturing infrastructure • Gives control to the driver • But driver comfort an issue with increasing traffic density Hence automation must be considered
- 18. Automated Manual Transmission(AMT) • Automation of Clutch and Gear shifting operations • Elimination of Clutch Pedal • Modification of Gear Shifting lever • Minimum modifications in manual transmission
- 19. AMT Features • Automationof Clutch operation and Gear shifting. • Clutch slip control during starting • Hill start aid system which will assist the driver in hold and move the vehicle in hill slope • Necessary fail safe systems such as sudden shifting from higher gear to lowest gear and vice versa
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- 21. Clutch Actuation Control •Engine Start - Starter should be operated only when the gear is in neutral position - When engine is not running and in power on, ECU will disengage clutch - When engine speed exceeds a specified rpm, ECU engages clutch gradually • Vehicle Start - On pressing the accelerator pedal, ECU controls the clutch - actuator travel and clutch engagement
- 22. Clutch Actuation Control •Gear Change - While engaging the clutch after gear shift, the ECU determines clutch actuator travel based on shifted gear position and accelerator pedal stroke • Clutch disengagement - While gear shifting and when accelerator pedal is released, - if the vehicle speed is lower than a set speed for select gear position, the ECU disengages clutch
- 23. Advantages of AMT •Reduced driver effort • Improved Clutch life • Utilization of existing manufacturing facilities for manual transmission • Lower production cost than automatic transmissions • Higher efficiency than automatic transmissions
- 24. Automatic Transmission (AT) ConventionalDefinition • Moving away from rest - Torque converter • Achieving ratio change - Planetary gear sets • No power interruption • Mechanism for ratio change - Wet plate clutches and brakes • Control of ratio change - Normally automatic timing and actuation
- 25. Fluid Coupling • Convertsor transmits rotating mechanical energy or power. • Basic components. - outer shell or housing, - impeller or pump and turbine or runner • Both of these units are contained within the housing via oil-tight seals. • The input turbine is connected to the power supply, typically an electric or ICE. • The output turbine is connected to the drive train of the vehicle or the drive system of a machine. • Mineral oil is used
- 26. Fluid Coupling: Working •Standstill - The entire operating fluid in the coupling is at rest • Idling - In sufficient centrifugal force for the oil to turn the turbine • Low to medium speed: - Centrifugal force pushes oil into turbine and some turning effort is transmitted. Large degree of slip in the unit. O/p shaft is rotating slowly than input shaft. • Medium to High Speed - Oil force is sufficient to transmit full power. O/p shaft rotating at about 98% of speed of I/p shaft (2% slip).
- 27. Torque Convertor • Servesas automatic clutch which transmits engine torque to the transmission input shaft • Multiplies torque generated by the engine • Absorbs torsional vibration of engine • Acts as a flywheel and smoothes out engine rotation • Drives oil pump • A torque converter consists of - Impeller - Turbine - Stator - and transmission fluid
- 28. Torque Convertor -Sectional View
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- 32. Working of TorqueConvertor Vehicle accelerates
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- 34. Planetary Gear System:Construction • Input shaft is connected to Ring gear(Blue) • Output shaft is connected to Plane carrier(Green) which is also connected to Multi-disk clutch • Sun gear is connected to a Drum(Yellow), which can be locked by brake band (Red). It is also connected to the other half of Clutch
- 35. Planetary Gear System:Operation • In Neutral • Both band and clutch sets are released • Planets assembled to carrier with NRB • Ring gear only drive planet gear not the planet carrier (Output shaft) • The planet gears drive the sun gears to spin freely
- 36. Planetary Gear System:Operation • In Low Gear (forward reduction) • Band locks the sun gear by locking the drum • Planets walk around the sun gear • Planet carrier to spin in same direction as ring gear • Gear ratio= sun & ring teeth/no of teeth of ring gear
- 37. Planetary Gear System:Operation • In High Gear (Direct drive) • Band is released. • Lock any two members • Clutch is engaged so that the sun gear and planet carrier is locked to act as a rigid member • Planets has to walk around the ring gear, • Ring Gear (Input shaft) will spin at the same speed as the Planet Carrier (Output shaft)
- 38. Planetary Gear System:Operation • Reverse Gear • Planet carrier is locked • Ring gear (Input shaft) will cause the sun gear (Output Shaft) to turn in the opposite direction
- 39. Automatic Transmission (AT) Advantages Theonly option for comfortable automatic shifting Cost issue mitigated by high volume manufacturing Disadvantages Cost for development and manufacturing Fuel economy due to torque converter Lack of control by the driver Modern improvements Better control algorithms Torque converter lock up Most useable transmissions based on a couple of standard arrangements Ravigneaux Lepelletier
- 40. Continuously Variable Transmission (CVT) •CVT provides infinite number of gear ratios (between a minimum & a maximum). • Shifts automatically with an infinite number of ratios • Seamless power delivery, no torque interruption & power loss
- 41. CVT: Construction Usesa pair of axially adjustable sets of pulley halves (Variators) Both pulleys have one fixed and one adjustable pulley halve A “belt” is used to transfers the engine's power from one shaft to another
- 42. CVT: Functioning • Thetransmission ratio is varied by adjusting the spacing between the pulleys in line with the circumference of the tapered pulley halves. • The variators are adjusted hydraulically. • When one pulley is varied, the other pulley must adapt itself inversely since the length of the belt is fixed.
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- 45. Basic Dual WetClutch
- 46. How DCT Works? In a conventional manual transmission, there is not a continuous flow of power from the engine to the wheels. Instead, power delivery changes from ON to OFF to ON during gearshift, causing a phenomenon known as "shift shock" or "torque interrupt A dual-clutch transmission uses two clutches, but has no clutch pedal. Sophisticated electronics and hydraulics control the clutches, just as they do in a standard automatic transmission. In a DCT, however, the clutches operate independently One clutch controls the odd gears(first, third, fifth and reverse), while the other controls the even gears (second, fourth and sixth) Using this arrangement, gears can be changed without interrupting the power flow from the engine to the transmission
- 47. Propeller Shaft Itpropels the vehicle forward, so called propeller shaft A Propeller Shaft connects a gearbox to a Differential. It is used to transmit the drive force generated by the engine to the axles. It is strong enough to handle maximum low gear torque It is provided with two U-joints to maintain constant velocity and positioning of differential at different plane. It is provided with a slip joint to take care of the change in length. Shaft diameter and its thickness decides the torque carrying capacity and angle of operation.
- 48. Propeller Shaft Singlepiece Two piece Front engine rear wheel drive Reduction in car height (lowering of body) Crash energy management Material Aluminum steel Composite (75% carbon, 25% glass-fibre with bonded steel end fittings- Renault) Cold rolled and seam welded
- 49. Universal joints • Designedto eliminate torque and speed fluctuations (constant velocity joints) • If only one universal joint is used, speed fluctuations will not be neutralized. • To maintain uniform motion, two universal joints are used with yoke lugs in phase.
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- 51. Differential • To transferthe engine power to the wheels • To act as the final gear reduction in the vehicle • To make the wheels to rotate at different speeds while negotiating a turn.
- 52. Differential: In StraightAhead Motion Input torque is applied to the ring gear, which turns the entire carrier, providing torque to both side gears, which in turn may drive the left and right wheels. If the resistance at both wheels is equal, the pinion gear does not rotate, and both wheels turn at the same rate.
- 53. Differential: In aTurn • If the left side gear (red) encounters resistance, the pinion gear(green) rotates about the left side gear, in turn applying extra rotation to the right side gear (yellow).
- 54. Axle Transmits rotarymotion and torque from the engine-transmission-driveshaft to the wheels Changes torsional direction from longitudinal to transverse Provides speed reduction and torque multiplication Provides a differential action to permit vehicle cornering Provides mounting points for suspension and brakes
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