Automotive Transmission system

SRI KRISHNA COLLEGE OF ENGINEERING AND TECHNOLOGY
DEPARTMENT OF MECHATRONICS ENGINEERING
Session: Introduction to Transmission
System
11/24/2020 16MT407 - Theory of Automobile Engineering 1
MODULE 2

SESSION OBJECTIVES
 On the completion of this session, the students might
be able to understand,
 Basic Necessity of a transmission system in Vehicle
 How the transmission system provide tractive force
to the vehicle.

Topics
 Function of Transmission system
 Basic Necessity of transmission
 Types of gears and Gear train
 Types of transmission

FUNCTION OF TRANSMISSION SYSTEM
Introduction:
 Engine is the only source to give
motive force to the vehicle
 This will help the vehicle to move on
different driving conditions from start
up to high speed driving
 It will ensure by transmission system
 The transmission is actually a set of
gears which is used to transfer the
power developed in the engine to
the driving wheels according to the
requirement's.

FUNCTION OF TRANSMISSION SYSTEM
Function of transmission system:
 It transfer the engine output power
to the final driven gear from where it
is transmitted to the driving wheels
through the drive shaft (or propeller
shaft)
 It provides sufficient torque
 It provides low to high speed driving
capability
 It is used to change the direction of
the wheel rotation

BASIC NECESSITY OF GEAR BOX
Transmission Necessity :
CAD B
OA – Stabilizing speed

TYPES OF GEARS
Introduction:
 Gears are toothed wheels that
transmit power between the shafts.
 The teeth my be cut on the edge on
the wheel on the side or inside.
 To transmit power, a gear on one
shaft is meshed with gear on
another shaft.
 The meaning of mesh is that the
teeth of a gear fit into the space
between the teeth on the another
gear

TYPES OF GEARS
Introduction:
 When one gear turns, then it’s teeth
forces the other gear to turn.
 The gear that does the turning is the
driving gear.[A - Gear]
 The gear that is forced to turn is the
driven gear.[B – Gear]

TYPES OF GEARS
Types of Gears: Spur Gears
 The spur gears are the most
common type of gears.
 These gears have teeth parallel to
the axis of wheel

TYPES OF GEARS
Types of Gears: Helical Gears
 It is very similar to spur gears.
 Gears having teeth inclined to the
axis of the wheel
 Angle of teeth give gears more tooth
contact in the same area.
 Also used to transmit power between
non parallel shaft.
 Running is quitter and smoother
than spur gears.
 This is Due to the increased number
of teeth in constant contact at any
one period of time.

TYPES OF GEARS
Types of Gears: Herringbone gears
 Double helical gears are known as
herringbone gears.
 The herring bone gear resemble two
helical gears that have been placed
side by side
 Advantage: To eliminate side thrust
issues in helical gears.

TYPES OF GEARS
Types of Gears: Bevel Gears
 The Bevel gears are used mostly in
situations that require power to be
transmitted at right angles.
 The bevel gears can have different
angle of application but tend to be
90o.

TYPES OF GEARS
Types of Gears: Worm Gears
 The worm gears are used to transmit
power at 90o and where high
reduction are required.
 It simply resembles a thread that
rides in concave or helical teeth.
Worm Gear
Worm Wheel

TYPES OF GEARS
Types of Gears: Rack & Pinion gears
 A rack & Pinion gear is basically used
to transmit power and motion in a
linear movement.

TYPES OF GEARS
Types of Gears: Planetary Gears
 The planetary gears consist of one or
more outer gears, revolving about a
central gear (or sun gear).
 Typically, the planet gears are
mounted on a movable arm which
itself may rotate relative to the sun
gear.
 The planet gear systems also
incorporate the use of an outer ring
gear, which meshes with planet
gears.

TYPES OF GEARS
Gear Ratio:
 The gear ratio’s are used to express the mathematical relationship between
the gears.
 The actual operation performed by the gear lever in an automobile is to
change the gear size
𝐺𝑒𝑎𝑟 𝑅𝑎𝑡𝑖𝑜 =
𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑡ℎ𝑒 𝑑𝑟𝑖𝑣𝑒𝑛 𝑔𝑒𝑎𝑟
𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑡ℎ𝑒 𝐷𝑟𝑖𝑣𝑒 𝑔𝑒𝑎𝑟

TYPES OF GEARS
Gear Ratio:
 When a larger gear is driven by a smaller gear, the speed of rotation on the
driving gear is reduced on the driven gear while the torque is increase
contrarily.

TYPES OF GEARS
Gear Ratio:
 When a small gear is driven by the larger gear, the result will be a decrease in
torque and an increase in speed.

TYPES OF GEAR TRAIN
Gear Train:
 Sometimes two or more
gears are made to mesh
with each other to
transmit power.
 This is called Gear train
 Types of gear train:
 Simple Gear train
 Compound gear train

TYPES OF GEAR TRAIN
Simple Gear Train:
 When there is only one gear on each shaft is known as simple gear train
 In here the motion of the driven gear is opposite to the motion of the driving
gear.

TYPES OF GEAR TRAIN
Simple Gear Train:
Speed ratio :
 Ratio of the speed of the driving
gear to the speed of the driven
gear and this ratio is inversely
related to the teeth on each
gears.
𝑆𝑝𝑒𝑒𝑑 𝑅𝑎𝑡𝑖𝑜 =
𝑆𝑝𝑒𝑒𝑑 𝑜𝑓 𝑓𝑖𝑟𝑠𝑡 𝑑𝑟𝑖𝑣𝑒𝑟
𝑆𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑑𝑟𝑖𝑣𝑒𝑛
=
𝑁𝑜. 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑑𝑟𝑖𝑣𝑒𝑛
𝑁𝑜. 𝑜𝑓 𝑇𝑒𝑒𝑡ℎ 𝑜𝑛 𝑑𝑟𝑖𝑣𝑒𝑟
𝑁1
𝑁2
×
𝑁2
𝑁3
=
𝑇2
𝑇1
×
𝑇3
𝑇2
𝑁1
𝑁3
=
𝑇3
𝑇1

TYPES OF GEAR TRAIN
Compound Gear Train:
 When there are more than one
gear on a shaft it is called a
compound Train of Gear.
𝑆𝑝𝑒𝑒𝑑 𝑅𝑎𝑡𝑖𝑜 =
𝑆𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑖𝑟𝑠𝑡 𝑑𝑟𝑖𝑣𝑒𝑟
𝑆𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑙𝑎𝑠𝑡 𝑑𝑟𝑖𝑣𝑒𝑛 𝑜𝑟 𝑓𝑜𝑙𝑙𝑜𝑤𝑒𝑟
=
𝑃𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑁𝑜. 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑑𝑟𝑖𝑣𝑒𝑛𝑠
𝑃𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑁𝑜. 𝑜𝑓 𝑇𝑒𝑒𝑡ℎ 𝑜𝑛 𝑑𝑟𝑖𝑣𝑒𝑟𝑠
𝑁1
𝑁2
×
𝑁3
𝑁4
=
𝑇2
𝑇1
×
𝑇4
𝑇3
𝑁1
𝑁4
=
𝑇2 × 𝑇4
𝑇1 × 𝑇3

TYPES OF GEAR TRAIN
Compound Gear Train: Advantage
 Compare to simple gear train much
larger speed reduction is achieved
 But simple gear require large size
gear at last for large speed reduction.

TYPES OF TRANSMISSION
Epicyclic or planetary
Type
Selective Type Progressive Type
Types of transmission:
 Sliding Mesh
transmission
 Constant mesh
Transmission
 Synchromesh
transmission

What is selective type transmission :
 Any speed may be selected from the neutral
position.
 Forward & Reverse gear always starts from
Neutral gear.
Constant Mesh
Sliding Mesh
SYNCHROMESH

What is Progressive type transmission :
 It is used in motor cycles
 The gears pass through the intervening
speeds while shifting one speed to another.
 There is neutral position between two gear
positions
NEUTRAL
NEUTRAL
NEUTRAL
1234

What is Epicyclic or Planetary transmission :
 An Epicyclic transmission consists of two
Epicyclic or planetary gear sets.

Sliding Mesh Gear box : Neutral condition
 Simplest type of transmission
 Name suggests by gears are changed by sliding one gear on the other.
 Main shaft not rotate on neutral condition – No power Transmission to wheels

Sliding Mesh Gear box : First Gear condition
 The direction of rotation of main shaft is same as that of the clutch shaft.
 Main shaft larger gear & Counter shaft smaller gears are meshed
 Hence speed reduction is 3:1.
 At differential on wheel side achieved as 12:1.

Sliding Mesh Gear box : Second gear condition
 The direction of rotation of main shaft is same as that of the clutch shaft.
 Main shaft smaller gear & Counter larger gears are meshed
 Hence speed reduction is 2:1.
 At differential on wheel side achieved as 8:1.

Sliding Mesh Gear box : Third gear condition
 The main shaft is slided axially towards the clutch shaft
 So that main shaft is directly connected to the clutch shaft.
 Main shaft & Clutch shaft runs at same speed.
 Speed reduction at gear 1:1 & at differential 4:1

Sliding Mesh Gear box : Reverse gear condition
 The larger (reverse) gear of the main shaft meshes with the reverse idler
gear.
 The reverse idler gear is always connected to reverse gear on counter shaft.
 Idler gear causes the main shaft rotates in opposite direction.

Sliding Mesh Gear box :
Advantages :
 It is simple in construction
 It has low cost
 The mechanical efficiency of sliding mesh gear box is very high
Disadvantage:
 The gear noise is very high due to the type of gears (i.e spur gears)
 It is difficult to obtain a smooth, quiet and quick change of gears.

CONSTANT MESH TRANSMISSION : Neutral condition
 Drive and driven gear combination for each speed, are constantly engaged
with each other.
 It will happen even in the neutral position, all gear combination are in mesh
and turning
 No power transmitted, because of gears on main shaft has freely rotate on
main shaft.

CONSTANT MESH TRANSMISSION : First Gear
 Dog clutches can be slided to achieve the power flow.
 The axial motion of dog clutch can achieved by providing the splines on main
shaft.
 D2 moves left & engage with Gear E to transfer power to wheels through
Main shaft
 Power Flow: A-B-
Layshaft-F-E-D2-
Mainshaft.

CONSTANT MESH TRANSMISSION : Second Gear
 D1 moves right & engage with Gear D to transfer power to wheels through
Main shaft

CONSTANT MESH TRANSMISSION : Third Gear
 D1 moves left & engage with Clutch Gear A to transfer power to wheels
through Main shaft
 Power Flow : A-D1-Main shaft

CONSTANT MESH TRANSMISSION : Reverse Gear
 D2 moves Right & engage with Gear I to transfer power to wheels through
Main shaft
 Power Flow : A-B-Layshaft-G-H-I-D2-Mainshaft.

CONSTANT MESH TRANSMISSION :advantage
 These have high Mechanical efficiency.
 It has helical gears, very quiet power transmission is achieved.
 Constant mesh ensure the safeness of gear from damage
Disadvantage:
 Dog clutch produce noise & jerk.

CONSTANT MESH
TRANSMISSION : Double
Declutching
 Smooth engage of dog
clutches should achieved
for good transmission.
 For this speed of the
main shaft gear & the
sliding dog must be
equal.
 This requires double
declutching.

CONSTANT MESH TRANSMISSION : Double Declutching – Working
 Clutch is disengaged (First Declutching) and the gear system is brought to
neutral position.

 Clutch is engaged and accelerator pedal is pressed to increase the speed of
main shaft gears.

 Clutch is disengaged once again (i.e., second declutching). The gear is
moved to the required lower gear and the clutch is engaged.
 In this process, the clutch is disengaged twice, therefore, it is called as
double declutching

SYNCHROMESH TRANSMISSIONS :
 Kind of constant Mesh transmission
 Gears on the main shaft are constant
mesh with gears on lay shaft
 The gears on the counter shaft are
fixed where as the gears on the main
shaft are free to rotate on the same
 Here instead of Dog clutch, a special
mechanism used called synchromesh
mechanism.
 Which is used frictional force during
shifting to mesh the to different
gears rotate at different speed.

SYNCHROMESH
TRANSMISSIONS :
PRINCIPLE
 Bringing to the
neutral state: For gear
changing from 3rd to 4th
 The clutch is
disengaged to stop
power flow from
the engine

SYNCHROMESH
TRANSMISSIONS :
PRINCIPLE
 Start of
synchronization:
 The sleeve move
on shifting direction
 And strut also
move on same
direction
 It forces the ring
into the cone shape
of Gear portion.

SYNCHROMESH
TRANSMISSIONS :
PRINCIPLE
 Midway through
synchronization:
 Further movement
make the sleeve to
over come the
force of spring
 It means sleeve &
projection of key
will disengaged

SYNCHROMESH
TRANSMISSIONS :
PRINCIPLE
 End of
synchronization:
 The sleeve directly
pushes
synchronizer ring
without key
operation
 The ring is strongly
pressed to the third
gear cone part with
great friction

SYNCHROMESH
TRANSMISSIONS :
PRINCIPLE
 End of
synchronization:
 Now the speed of
the hub sleeve and
the gear becomes
equal.
 Results in hub
sleeve splines mesh
with the
synchronizer ring
splines.

SYNCHROMESH
TRANSMISSIONS :
PRINCIPLE
 End of shift change:
 After the hub
sleeve spline
meshes with
synchronizer ring
splines
 Now the hub sleeve
moves further and
meshes with the
gear spline.

FLUID COUPLING:
 It is called us
Hydrodynamic Device
 Used to transmit
rotating mechanical
power
 And an alternative to
Clutch.
 Fluid coupling
performs the transfer
of torque in a fashion
which is similar to the
transfer of motion by
fans.

FLUID COUPLING:
 Flow of air at outside fan B still
possesses a considerable
amount of energy
 And if ducts are used to
redirect this air flow to rear of
the vanes in fan A.
 Then the rotation of that fan
will be assisted and torque will
be increased.

FLUID COUPLING: Like Mechanical
Clutch
 The pump is typically connected to
the fly wheel of the engine.
 The turbine is connected to the input
shaft of transmission
 The torque is transferred from the
engine to transmission system with
the help of fluid motion for propelling
the vehicle.

FLUID COUPLING: Construction of
Fluid coupling
 Pump : Called as driving impeller,
which will be mounted over the
input shaft.
 Turbine : Driven impeller which
will be mounted over the output
shaft.
 Housing: Provide the oil tight seal
& Protect the Pump & Turbine

FLUID COUPLING: Working
 No mechanical interconnection b/n
Rotor & Impeller.
 Power transmitted by the virtue`
of fluid filled in the coupling
 Engine drives the impeller, which
imparts the velocity & energy to
the fluid.
 Thus will converted into Mechanical
energy in the rotor thus rotating it.

 The fluid flows a closed circuit of flow from impeller to rotor through the air
gap at the outer periphery.

 And then from the rotor to the impeller through the inner periphery.

 As the slip increases more & more fluid can be transferred from the impeller
to the rotor and more torque is transmitted.
𝑆𝑙𝑖𝑝 =
𝐷𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝑜𝑓 ℎ𝑒𝑎𝑡 𝑏𝑒𝑡𝑤𝑒𝑒𝑛 𝑡ℎ𝑒 𝑟𝑜𝑡𝑜𝑟 & 𝐼𝑚𝑝𝑒𝑙𝑙𝑒𝑟
𝐷𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝑜𝑓 𝑠𝑝𝑒𝑒𝑑 𝑏𝑒𝑡𝑤𝑒𝑒𝑛 𝑟𝑜𝑡𝑜𝑟 & 𝐼𝑚𝑝𝑒𝑙𝑙𝑒𝑟

Torque Converter:
 Type of fluid coupling
 It increase the torque of
the vehicle by reducing
the speed.
 Provides continuous
variation from low to
high.
 Key characteristic –
Ability to multiply torque
when there is a
substantial difference
b/n input & output
rotational speed.

Torque Converter:
 It is equivalent of a reduction gear.
 Helps to automatic transmission to
disengage transmission to change
gear

Torque Converter: Stator
 The stator is located b/n
Pump & Turbine.
 Modified the direction of
fluid comes out from
turbine
 Prevent hard impact of
Pump impeller
 The stator vanes catches
the fluid from turbine &
redirects to the pump
impeller, for giving the
added torque

Torque Converter: Stator
 The stator is mounted to
the stator shaft, which is
fixed to the transmission
case.
 One way clutch mounted
to the stator allows it to
rotate in the same
direction as the engine
crank shaft
 Because of the fluid flow,
if the stator rotates in
fluid direction, it will stop
by one way clutch

Automatic
Transmission:
 Most advanced system
 Reduce the mechanical
efforts very much
 Different speeds are
obtained automatically.
 Called as hydramatic
transmission.
 It contains Epicyclic
gear arrangement, Fluid
Coupling and torque
converter.

Automatic Transmission:
Planetry gearing:
 Consists of one or more
outer gears, or planet gears
revolving about a central
Gear.
 Different torque ratio can
achieved
 Very compact

Automatic Transmission: Working
 Planetry gear set contains 2 Input
& One output
 Input one – Ring Gear
 Input Two – Sun gear
 Output – Connected to Planet
carrier, which hold the planet Gear.

Working
 Now Ring gear is stationary
 Sun gear is rotating, causes the
Planetry gear to rotate
 Transmit the power to the
output shaft to drive the wheel.

Working
 Now Ring gear is also Rotates.
 Planet gears revolves & Spin
 So, the output speed further
increases.

Working
 Now Ring gear & sun gear
rotates at same speed.
 Whole mechanism moves as
a single unit.
 Planet gear do not spin, But
revolves around sun gear.
 Output speed = Input speed

Working
 Ring gear speed is further
increased.
 It cause the output speed to
increase more

Working
 Now sun gear rotates in
opposite direction
 Reverse gears occurred.
 The operation of automatic
transmission is all about
the different rotational
speed of ring & sun gear.

Working
 Clutch packs C1 & C5
used for transmitting
power.
 Clutch packs External
teeth connects case &
Internal teeth connects
hub.
 Intermediate shaft is
used for connects input
shaft & output shaft.

Working
 By Engaging C1 & C5,
First gear will engage.

Working
 For increasing the gear
ratio, New Planetry gear
will add with C4.
 The second planet carrier
permanently contact with
first one.
 Input drives both sun
gear at speed of it
 Planet carrier
permanently connect
with first one.

Working
 By enabling the C1 &
C4,the gear two will
occur
 This cause the first ring
Gear to rotate.
 Gear 2 will occur

Working
 Planet carriers always
connect with hollow
shaft.
 The hollow shaft engage
by C2 with housing.
 For direct drive the ring
& sun gear should rotate
at same speed of input
shaft.

Working
 By engaging the C1 &
C2, the Fourth gear will
occurred.

Working
 Input rotational is given
to planet carrier & Ring
gear will stationary.
 By enabling the C2 & C4
can achieve the over
drive called 6th gear.

Working
 For achieving remaining
gears, additional
planetary gears are
added (Set 3)
 In set 3, the C3 will lock
the 3rd ring gear & driven
the set 2, set 1
 By enabling C1 & C3, the
third gear will occur.

Working
 Now C2 & C3 applied for
Gear 5.

Automatic Transmission: Stages
 Park(p): Lock the transmission,
restrict the vehicle from moving
 Reverse(R): selecting it to allow it
reverse the car.
 Neutral(N): Disconnects the
transmission from wheel
 Low(L): Selecting it allow you drive
in lower speed ratio – It required in
drive the vehicle in hilly/Midway
areas
 Drive(D): By selecting it allow the
vehicle to move and accelerate
through a range of gears

Manual Transmission vs Automatic Transmission
Manual Transmission Automatic Transmission
Cheaper Costlier than manual transmission
Better fuel economy, because of better
mechanical & gear train efficiency
Not have the better fuel economy, because
of not have the better gear train &
mechanical efficiency
It requires more driver control Does not offer more driver control

END

Automotive Transmission system

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