Automotive Transmission: U5AUA11 By. B.HARISH BABU Asst - Prof, Vtu
Automotive Transmission: U5AUA11 By. B.HARISH BABU Asst - Prof, Vtu
Automotive Transmission: U5AUA11 By. B.HARISH BABU Asst - Prof, Vtu
U5AUA11
By.
B.HARISH BABU asst.prof ,vtu.
UNIT I
Contents
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
6
Transmission Types
7
Clutch
Function of clutch
• Clutch is used to disengage and engage the
engine with rest of the transmission systems.
8
Clutch
Requirement of Clutch
• Transmit maximum torque of the engine.
• Dynamically balanced.
• As small as possible.
• Easy to operate.
9
Clutch Unit
• Flywheel also acts as a driving
member
• 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.
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
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
• Cheap to make
• Durable, efficient
• Easy to install
• Elimination of Clutch
Pedal
• Modification of Gear
Shifting lever
• Minimum
modifications in
manual transmission
21
AMT Features
• Automation of Clutch operation and Gear
shifting.
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
26
Automatic Transmission (AT)
Conventional Definition
• Moving away from rest - Torque converter
• No power interruption
• 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
42
Continuously Variable Transmission
(CVT)
• CVT provides infinite
number of gear ratios
(between a minimum & a
maximum).
• Seamless power
delivery, no torque
interruption & power loss
43
CVT: Construction
Uses a pair of axially
adjustable sets of
pulley halves
(Variators)
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
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
• Designed to eliminate
torque and speed
fluctuations (constant
velocity joints)
• To maintain uniform
motion, two universal joints
are used with yoke lugs in
phase.
53
Universal joints
54
Hooke‟s Joint
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.
2005 2010
3%
7% 10% MT
AT
43%
CVT
DCT
37%
AMT
2015
Requirements of the Transmission
Design Process
Product Life Cycle
64
Stages in the Design Process
• Timeline
Project set up
Concept design
Detail design
Tolerancing &
drawings
Prototype testing
65
UNIT V
Project Set Up
- The first stage of the design process is to set
targets
Market Existing product knowledge
research Product Design Specification
Standards
Load data (PDS)
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
history for the 95th damage for each appropriate for
centile component in the transmission design
transmission
72
Concept Design
• Activities within Concept Design (part A)
Design gear Synchroniser Spline
teeth and design, sizing design
blanks and and and
Inputs from dog teeth packaging rating
PDS:
•Gear ratios Can
Create ratios Yes Output:
•Engine
torque and initial Iterative Design and Proposed
duty cycle gearbox of the Gearbox packagin concept
•3D concept 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
74
Concept Design
Iterative Design, Analysis and Optimisation, by CAE:
- Gears - Synchronizers
• Tooth numbers • Shift force
• Rating to ISO 6336 • Cone to index torque
• Contact Ratio targets ratio
• Misalignment targets
- Bearings
- Shaft • Durability
• Durability • Misalignment targets
• Deflection
- Spline
• Stress
75
Concept Design
• Activities within Concept Design (part B)
Casing
Design and
Differential
Shift
Proposed Concept Layout
Mechanism
Check for Completed
compatibility
Concept
with and with
other vehicle
components
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
77
Concept Selection
• Concept scoring
• Assign a score to each concept according to the
extent to which it meets each requirement
• 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
geometry Design
Detailing
Completed
FE, System Deflection
Detailed
and Gear Tooth Design, all
Completed Concept Design Casing Detailing
Contact Detailed Nominal
Analysis
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
81
Analysis Methods
• Principles
86
Engineering Drawings and Tolerancing
87
Engineering Drawings and Tolerancing
• Tolerance Stacks
Identify
checks required
Gear and shaft
Create master
dimension sheet
deflections from
analysis
Final design
Create tolerance
stacks for each
shaft assembly Yes
Revise dimensions
Check result No on master No Check result
dimension sheet
Yes No
Create tolerance
Create housing
stacks for shaft to Check result Yes
tolerance stacks
shaft clearances
88
Engineering Drawings and Tolerancing
Potential Problems
- 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)
91
THANK YOU