Automotive Transmission U5AUA11 By. B.HARISH BABU asst.prof ,vtu.

UNIT I

Contents  Propeller Shaft  Introduction  Transmission Systems  Manual  Automated Manual  Automatic  Continuously variable  Dual Clutch  Propeller Shaft 2

Contents  Universal joints  Differential  Requirements of the Transmission Design Process  Product Life Cycle  Stages in the Design Process • Project Set Up • Concept Design • Detailed Design • Engineering Drawings and Tolerancing 3

Transmission System • Function of transmission: - It is used to transmit engine torque to the driving wheels to drive the vehicle on the road. 4

Requirement of Transmission System • 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 5

Transmission System - Layout 6

Transmission Types 7

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. 8

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. 9

Clutch Unit • Flywheel also 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.

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 11

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 12

Clutch Material 13

Need of Gear Box 14

Gear Box • Gear box 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. 15

Manual Transmission - Types 16

UNIT II

Synchronizers • A device used 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. 17

Synchromesh Gearbox 18 1.I speed gear 2.II speed gear 3.main shaft 4.outer engaging unit 5.inner engaging unit 6.top gear engaging teeth 7.main drive gear 8.top gear synchronizing cones 9.counter shaft 18

How Manual Transmission Work? • 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. 19

Manual Transmission Hence automation must be considered • Cheap to 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 20

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 21

AMT Features versa • Automation of 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 22

System Block Diagram 23

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 24

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 25

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 26

Automatic Transmission (AT) Conventional Definition • 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 27

Fluid Coupling • Converts or 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 28

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). 29

UNIT III

Torque Convertor • Serves as 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 30

Torque Convertor - Sectional View 31

Impeller 32

Turbine 33

Stator 34

Working of Torque Convertor Vehicle accelerates 35

Planetary Gear System 36

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 37

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 38

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 39

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) 40

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 41

UNIT IV

Automatic Transmission (AT) Advantages The only 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 42

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 43

CVT: Construction  Uses a 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 44

CVT: Functioning • The transmission 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.

Dual Clutch Transmission (DCT) 46

DCT: Construction

Basic Dual Wet Clutch

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 49

Propeller Shaft Single piece  Aluminum  steel  Single piece  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 50

Propeller Shaft  It propels 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. 51

Propeller Shaft • Design requirements • Critical speed is at least 15% above top speed • Torque carrying capacity requirements • Plunge requirements (suspension travel) • Assembly requirements 52

Universal joints torque and speed fluctuations (constant • Designed to 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. 53

Universal joints 54

Hooke‟s Joint Condition for Constant velocity drive with two Hooke’s joint 55

Differential transfer the engine power to the wheels speeds while • To act as the final gear reduction in the vehicle • To make the wheels to rotate at different speeds while negotiating a turn. 56

Differential: In Straight Ahead 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. 57

Differential: In a Turn • 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). 58

Axle  Transmits rotary motion 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 59

Transmission Troubleshooting • Leaking Transmission Fluid • Slipping of Transmission • Damaged Transmission Fluid • Surging of Transmission • Gear Problems • Fluid Leaking • Spilling out of Fluid • Erratic Gear Shifting • Overheating of Transmission 60

Transmission Trend Passenger Car Transmission in India  Manual transmission is more dominant in India as compared to other types of transmissions.  Majority of the MT are using 5speed GB as compared to 6 speed GB.  But many of the luxurious car manufactures are now using AMT or T’s. Source: Mahr GmbH, Germany

Global Transmission Trend Estimated global market share (%) for passenger car transmission types 1% 2% 1% 2% 4% 6% MT MT AT AT 47% 50% CVT CVT 46% DCT 41% DCT AMT AMT 2005 2010 3% MT 7% 10% AT 43% CVT DCT 37% AMT 2015

Requirements of the Transmission Design Process

Product Life Cycle • Product Life Cycle must be developed to deliver Company goals New Product Introduction Prototype Manufacturing, Feasibility Studies/ Transmission Production Ready Product support and Design Development Transmission New Concepts development Market feedback, Market research, Technical Development, Application experience Research 64

Stages in the Design Process • Timeline Project set up Concept design Detail design Tolerancing & drawings Prototype testing 65

UNIT V

Project Set Up  Existing product knowledge  Standards - The first stage of the design process is to set targets  Market research  Existing product knowledge Product Design Specification  Standards  Load data  Customer specific requirements (PDS) - The PDS contains all the specification data and design targets • This document should be approved before work starts on concept design - The PDS is a „live‟ document • This means that changes can be made to it, providing all parties agree to them 66

Project Set Up To be included in the Product Design Specification: • Understanding the customer • Special considerations - Review all validation testing needs/wants from - - Customer PDS for unusual manoeuvres • Rig (Vehicle/Transmission) - Market Understanding • Vehicle - Prior Design Experience • Special environmental operation conditions, eg: • General Requirements - Number of gear ratios and their values - Very high or very low ambient temperature conditions - Packaging envelope constraints - Extremely tight vehicle packaging space - Weight • Special operational cycles, eg: - Unusual off-road usage - Application specifics - Duty cycle - Occasional vehicle overload operation - Interfaces • Gear ratio must be defined. 67

Project Set Up • To be included in the Product Design Specification: - It may not be possible to meet all requirements, so define the hierarchy of importance, normally (approximately): • Packaging within the vehicle • Assemble-ability • Durability • Ratio • Weight • Cost • Gear shift quality • Noise 68

Project Set Up To be included in the Product Design Specification: • Design Loads & Duty Cycles - A design load case may be comprised of a series of loads and cycles/time at those loads combined into a duty cycle definition • Design loads are typically modified somewhat - Maximum net engine output torque including • Reserve capacity for enhanced engine torque or larger engine application: 0% to 10% typical • Factor for unusually high engine torsionals output: 0% to 5% typical - Maximum vehicle skid torque • Max skid torque in each gear for operation on dry, new concrete • Usually only significant in lowest ratios (eg: 1st, Reverse) - Maximum transient overload torque (static overload only) • Factors vary according to specific vehicle and are generally based off of historical vehicle test results • Typical values range from 1.5x to 2.5x maximum engine torque 69

Project Set Up: Duty Cycle • A key component of the “targets” is the Duty Cycle. • What is a Duty Cycle? - Calculation of Component Reliability - single loadcase Material Properties Operating Conditions Select Required Reliability Analysis to Component Operating Analysis to predict Geometry Stresses predict life stress Applied Loads (Duty Cycle) 70

Project Set Up: Duty Cycle • A Duty Cycle is a collection of loadcases - All automotive transmissions are loaded with multiple loadcases - Multiple ratios - Different torque levels for each ratio • 10%, 20%, 30% … 100% torque • Accounting for Multiple-loadcases - Damage - “Miner‟s Rule” (Linear Damage Hypothesis) • To combine the effect of different loadcases • Damage Fraction & Percentage • We need to account for the effect of these many loadcases 71

Project Set Up: Duty Cycle • In-service Loads must be converted into a duty cycle for design and testing Durability In-Service Loads Calculation Design Duty Cycle Time/torque To derive the Equivalent duty cycle appropriate for history for the 95th centile damage for each component in the transmission transmission design Test Duty Cycle Equivalent duty cycle appropriate for rig testing 72

Concept Design • Activities within Concept Design (part A) 73 Design gear teeth and blanks and dog teeth Synchroniser design, sizing and Spline design and Inputs from rating packaging PDS: Can •Gear ratios Yes Output: Create ratios •Engine torque and duty cycle initial Iterative Design of the Gearbox Concept and Proposed gearbox packagin concept •3D concept g be layout packaging achieved space ? Define Define No shaft roller sections bearings 73

Concept Design • Generation of Design Options (Layouts/ Topology) - Create as many different design layouts as possible to meet the ratio and packaging requirements Option A Option B Option C Option D Option E Option F 74

Concept Design Iterative Design, Analysis and Optimisation, by CAE: - Gears - Synchronizers • Tooth numbers • Shift force • Rating to ISO 6336 • Cone to index torque ratio • Contact Ratio targets • Misalignment targets - Bearings - Shaft • Durability • Misalignment targets • Durability • Deflection - Spline • Stress 75

Concept Design • Activities within Concept Design (part B) Casing Design and Differential Shift Proposed Concept Layout Mechanism Check for compatibility with other components Completed Concept and with vehicle packaging; Check for Design Assembly Rank against PDS, other Iterate on items defined in Concept Design Part A if designs necessary • Once the concepts have been modelled and analysed, their strengths and weaknesses can be evaluated • The selected concept will then form the basis for the detailed design 76

Concept Selection • Evaluation criteria • List all the requirements for the design from the specification • Apply a weighting importance to each requirement (e.g. 1-5) • Determine what objective measures can be taken from concept model • Weight • Number of parts • Safety factors 77

Concept Selection • Concept scoring • Assign a score to each concept according to the extent to which it meets each requirement • Multiply each score by the appropriate weighting factor • The best scoring concept will then form the basis for the detail design 78

Detailed Design Activities within Detailed Design • Focus on system deflections and gear micro-geometry design Gear Micro- Differential Detailing geometry Design Completed Detailed Design, all FE, System Deflection and Gear Tooth Completed Concept Design Casing Detailing Contact Detailed Analysis Nominal Dimensions Complete Detailed Design and Analysis of Other Components; Lubrication system Check for compatibility with other components Iterate on Concept Design Parts A and B if necessary 79

Detailed Design • Calculation of System Deflections Load distribution Shaft deflection Load distribution factor Contact Stress Stress • Calculation of Durability 80

Detailed Design • Accurate analysis is required to determine whether targets are met • Simple methods do not give accurate results - Increased risk of problems later in product life cycle - Lack of clear direction for optimisation • Detailed analysis methods have their own issues - Many design options - Do we have to calculate everything before we make a decision? - How do we manage these methods in the design process? 81

Analysis Methods • Principles performance „hierarchy‟ of design - Hierarchy of design parameters • Understand how design parameters affect other design parameters and transmission performance • Understand the „hierarchy‟ of design parameters • Define the most important ones first

Analysis Methods • Hierarchy of Design Parameters - Some parameters have a big effect on gearbox performance - Some parameters are needed to define other parameters - e.g. gear centre distance Gear centre distance Gear tangential load Gear stress Gear durability Bearing load Bearing durability Housing design Housing stiffness Gear misalignment

Analysis Methods • Hierarchy of Design Parameters - Other parameters have a smaller effect on gearbox performance - They are dependent on preceding parameters being defined - e.g. gear micro-geometry Gear macro-geometry Gear centre distance Gear tangential load Gear tooth contact and transmission Gear micro-geometry error Housing design and stiffness Gear misalignment

Analysis Methods Seal design Gearbox packaging • Hierarchy of Design Parameters - Other parameters have little effect on the gearbox performance - They can be estimated Shaft design Seal - e.g. seal design design Gearbox packaging

Engineering Drawings and Tolerancing • Activities within Engineering Drawings and Tolerancing - Major issues should be resolved Complete Drawings Confirm for Components. Sub- Assembly and General Deliver Material Completed Specification Arrangement, with Assembly Instructions Drawings Identify All Carry out all tolerance stack calculation and Tolerance Stack Loops Completed Detailed Design assess Define Tolerances If tolerance stacks a problem, adjust tolerances if necessary If major problem iterate on Detailed Design if necessary 86

Engineering Drawings and Tolerancing • Applying Manufacturing Tolerances - Tolerances applied to components based on knowledge of manufacturing process • e.g. turning, grinding etc - Functionally critical features identified - Initial tolerances applied based on experience • These will be updated during the tolerance analysis 87

Engineering Drawings and Tolerancing • Tolerance Stacks Identify checks required Gear and shaft deflections from Create master dimension sheet Final design analysis Create tolerance stacks for each shaft assembly Yes Revise dimensions on master No Check result No Check result dimension sheet Yes No Create tolerance stacks for shaft to Create housing Check result Yes tolerance stacks shaft clearances 88

Engineering Drawings and Tolerancing Potential Problems • Form and functionality at tolerance extremes - Symptom (example): At tolerance extremes, transmission does not assemble or there is a foul (at zero load) - Action: Small iteration: Redefine the tolerances Large iteration: Nominal dimensions are redefined 89

Engineering Drawings and Tolerancing Potential Problems • Form and functionality at tolerance, temperature extremes, under load - Symptom (example): Transmission does not assemble or there is a foul at: • Tolerance extremes • Temperature extremes • Load (i.e. deflected shapes) - Example: Gears clash due to thermal expansion and axial movement due to compliance of bearings, housing etc. - Action (as before) 90

Output of Design Process • A layout that satisfies the key requirements of the PDS • All durability targets are met, including the effect of system deflections, at all tolerances, thermal extremes etc. • Bill of Materials and material selection list confirmed • 3D models complete with all components defined to nominal dimensions • 2D drawings of all components defined with tolerances • 2D drawings of sub-assemblies and assemblies, with assembly instructions 91

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