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Automotive Transmission

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Automotive Transmission U5AUA11 By. B.HARISH BABU asst.prof ,vtu. * Global Transmission Trend Estimated global market share (%) for passenger car transmission types 1 ... – PowerPoint PPT presentation

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Title: Automotive Transmission


1
Automotive Transmission
U5AUA11 By. B.HARISH BABU asst.prof ,vtu.
2
UNIT I
3
Contents
? 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
drivingwheels to drive the vehicle on the road.
4
6
Requirement of Transmission System
To provide for disconnecting the engine from
thedriving wheels
When engine is running , connect the
drivingwheels to engine smoothly without shock
Leverage between engine and driving wheels
tobe varied
Enable the driving wheels to rotate at
differentspeeds.
Provide relative movement between engine
anddriving wheels
5
7
Transmission System - Layout
6
8
Transmission Types
7
9
Clutch
Function of clutch
Clutch is used to disengage and engage
theengine with rest of the transmission systems.
To disengage while starting the engine
andwhile changing gear ratio.
To engage after starting of the engine and
gearshift 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 orHydraulic)
- 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 Flywheelface 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 - Types
16
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
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
Cheap to make
Durable, efficient
Easy to install
Established in marketplace and
withmanufacturing infrastructure
Gives control to the driver
But driver comfort an issue with increasing
trafficdensity
Hence automation must be considered
20
23
Automated Manual Transmission (AMT)
Automation
of
Clutch and Gear
shifting operations
Elimination of ClutchPedal
Modification of GearShifting lever
Minimum
modifications
in
manual transmission
21
24
AMT Features
Automation of Clutch operation and
Gearshifting.
Clutch slip control during starting
Hill start aid system which will assist the
driver inhold and move the vehicle in hill slope
Necessary fail safe systems such as
suddenshifting 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
isin neutral position
- When engine is not running and in power on,
ECUwill disengage clutch
- When engine speed exceeds a specified rpm,
ECUengages clutch gradually
Vehicle Start
- On pressing the accelerator pedal, ECU
controlsthe clutch
- actuator travel and clutch engagement
24
27
Clutch Actuation Control
Gear Change
- While engaging the clutch after
gearshift, the ECU determines clutch actuator
travel based on shifted gear position
andaccelerator pedal stroke
Clutch disengagement
- While gear shifting and when acceleratorpedal
is released,
- if the vehicle speed is lower than a setspeed
for select gear position, the ECU
disengages clutch
25
28
Advantages of AMT
Reduced driver effort
Improved Clutch life
Utilization of existing manufacturing
facilitiesfor manual transmission
Lower production cost than automatictransmissio
ns
Higher efficiency than automatictransmissions
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 View
31
35
Impeller
32
36
Turbine
33
37
Stator
34
38
Working of Torque Convertor
Vehicle accelerates
35
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
shiftingCost issue mitigated by high volume
manufacturing
Disadvantages
Cost for development and manufacturingFuel
economy due to torque converter
Lack of control by the driver
Modern improvements
Better control algorithmsTorque 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 amaximum).
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'spower 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
?
? Two piece
? Front engine rear wheel drive? Reduction in
car height (lowering of body)
? Crash energy management? Material
? Aluminum? steel
? Composite (75 carbon, 25glass-fibre with
bonded steelend fittings- Renault)
? Cold rolled and seamwelded
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 topspeed
Torque carrying capacity requirements
Plunge requirements (suspension travel)
Assembly requirements
52
57
Universal joints
Designed to eliminate
torque
and
speed
fluctuations
(constant
velocity joints)
If only one universal joint isused, speed
fluctuationswill 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
Hookes joint
55
60
Differential
To
transfer
the
engine power to the
wheels
To act as the finalgear reduction
inthe vehicle
To make the wheelsto 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 torqueto both side gears,
whichin turn may drive the leftand right
wheels.
? If the resistance at bothwheels is equal,
thepinion 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 piniongear(green) rotatesabout
the left sidegear, in turn applyingextra
rotation to the
right
side
gear
(yellow).
58
63
Axle
? Transmits rotary motion and torque from
theengine-transmission-driveshaft to the wheels
? Changes torsional direction from longitudinal
totransverse
? Provides speed reduction and
torquemultiplication
? Provides a differential action to permit
vehiclecornering
? Provides mounting points for suspension
andbrakes
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 Ts.
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
CVT
50 CVT
46
DCT
DCT
41
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
Manufacturing,
Prototype
Transmission Production Ready
Product support and
Feasibility Studies/
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
- 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
startson concept design
- The PDS is a live? document
This means that changes can be made to it,
providingall 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
- Extremely tight vehicle
- Packaging envelope constraints
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 engineapplication 0 to 10 typical
Factor for unusually high engine torsionals
output 0 to 5typical
- 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 generallybased 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
RequiredReliability
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
dutycycle for design and testing
Durability
In-Service Loads
Design Duty Cycle
Calculation
Time/torque
Equivalent duty cycle appropriate for
To derive the
history for the 95th centile
damage for each
transmission design
component in the transmission
Test Duty Cycle
Equivalent duty
cycle appropriate
for rig testing
72
78
Concept Design
Activities within Concept Design (part A)
Design gearteeth andblanks anddog teeth
Spline
Synchroniserdesign, sizingand
design
and
rating
Inputs from
packaging
PDS
Can
Gear ratios
Yes Output
ratios
Create
Engine
Proposed
Iterative Designof the GearboxConcept
initial
and
torque andduty cycle
concept
gearbox
packagin
layout
3D
g be
concept
packaging
achieved
space
?
No
Define
Define
shaft
roller
sections
bearings
73
79
Concept Design
Generation of Design Options (Layouts/
Topology)
- Create as many different design layouts as
possibleto 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
Cone to index torque ratio
Rating to ISO 6336
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 andDifferential
Shift
Proposed Concept Layout
Mechanism
Check for compatibilitywith other components
Completed
Concept
and with vehiclepackaging 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 thespecification
Apply a weighting importance to each
requirement(e.g. 1-5)
Determine what objective measures can be
takenfrom concept model
Weight
Number of parts
Safety factors
77
83
Concept Selection
Concept scoring
Assign a score to each concept according
to theextent to which it meets each requirement
Multiply each score by the appropriate
weightingfactor
The best scoring concept will then form the
basis forthe 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
DetailedDesign, all
FE, System Deflection and Gear Tooth
Casing Detailing
Completed Concept Design
Nominal
Contact Detailed Analysis
Dimensions Complete
Detailed Design and Analysis of Other
ComponentsLubrication system
Check for
compatibility withother components
Iterate on Concept DesignParts 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
- Hierarchy of design parameters
Understand how design parameters
affectother 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
gearboxperformance
- Some parameters are needed to define
otherparameters
- e.g. gear centre distance
Gear tangential load
Gear stress
Gear centre distance
Gear durability
Bearing load
Bearing durability
Housing design
Gear misalignment
Housing stiffness
89
Analysis Methods
Hierarchy of Design Parameters
- Other parameters have a smaller effect on
gearboxperformance
- They are dependent on preceding parameters
beingdefined
- 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
Hierarchy of Design Parameters
- Other parameters have little effect on
thegearbox 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
Arrangement, withAssembly Instructions
Specification
Drawings
Identify All
Carry out alltolerance stackcalculation and
ToleranceStack Loops
Completed Detailed Design
assess
If tolerance stacks a problem, adjust
Define Tolerances
tolerances if necessary
If major problem
iterate on DetailedDesign if necessary
86
92
Engineering Drawings and Tolerancing
Applying Manufacturing Tolerances
- Tolerances applied to components based
onknowledge of manufacturing process
e.g. turning, grinding etc
- Functionally critical features identified
- Initial tolerances applied based on experience
These will be updated during the
toleranceanalysis
87
93
Engineering Drawings and Tolerancing
Tolerance Stacks
Identify
checks required
Gear and shaftdeflections from
Create masterdimension 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 tolerancestacks 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
notassemble 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,
temperatureextremes, under load
- Symptom (example) Transmission does not
assembleor there is a foul at
Tolerance extremes
Temperature extremes
Load (i.e. deflected shapes)
- Example Gears clash due to thermal expansion
andaxial 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
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