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

2. UNIT I

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

4. 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

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

6. 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

7. Transmission System - Layout6

8. Transmission Types 7

9. 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

10. 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

11. 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.

12. 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

13. 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

14. Clutch Material 13

15. Need of Gear Box 14

16. 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

17. Manual Transmission - Types16

18. UNIT II

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. System Block Diagram 23

26. 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

27. 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

28. 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

29. 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

30. 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

31. 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

32. UNIT III

33. 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

34. Torque Convertor - Sectional View31

35. Impeller 32

36. Turbine 33

37. Stator 34

38. Working of Torque Convertor Vehicle accelerates35

39. Planetary Gear System 36

40. 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

41. 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

42. 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

43. 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

44. 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

45. UNIT IV

46. 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

47. 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

48. 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

49. 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.

50. Dual Clutch Transmission (DCT)46

51. DCT: Construction

52. Basic Dual Wet Clutch

53. 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

54. 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

55. 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

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

57. 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

58. Universal joints 54

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

60. 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

61. 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

62. 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

63. 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

64. 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

65. 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

66. 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

67. Requirements of the Transmission Design Process

68. 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

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

70. UNIT V

71. 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

72. 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

73. 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

74. 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

75. 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

76. 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

77. 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

78. 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

79. 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

80. 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

81. 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

82. 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

83. 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

84. 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

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

86. 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

87. 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

88. 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

89. 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

90. 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

91. 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

92. 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

93. 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

94. 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

95. 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

96. 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

97. THANK YOU