Unit-3-Transmission system of Automobile

AUTOMOBILE ENGINEERING
Unit-III- Transmission system of
Automobile
(Introduction & Clutches)
By,
Dr.S.SURESH,
Assistant Professor,
Department of Mechanical Engineering

TRANSMISSION SYSTEM
 It is used to transmit engine torque to the
driving wheels to drive the vehicle on the
road.

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
 Enable the driving wheels to rotate at different
speeds.
 Provide relative movement between engine and
driving wheels

TOPICS....
1. Clutch-types and construction,
2. Gear boxes- manual and automatic, gear shift
mechanisms,
3. Over drive, transfer box, fluid flywheel, torque
converter,
4. Propeller shaft, slip joints, universal joints,
5. Differential and rear axle,
6. Hotchkiss Drive and Torque Tube Drive.

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.

REQUIREMENT OF CLUTCH
 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.

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.

POSITIVE CLUTCH:
 The positive clutches are used when a positive drive is required.
 The simplest type of a positive clutch is a jaw or claw clutch.

POSITIVE CLUTCH:
 The jaw clutch permits one shaft to drive another
through a direct contact of interlocking jaws.
 It consists of two halves, one of which is permanently
fastened to the driving shaft . The other half of the
clutch is movable and it is free to slide axially on the
driven shaft, but it is prevented from turning
relatively to its shaft.

DISADVANTAGE OF POSITIVE CLUTCH :
❖ Positive clutch constitutes the action of engaging and
disengaging through mating surfaces.
❖ Bringing two rotating parts to mate together at a
very high rpm is very difficult and so normally
during the engaging and disengaging the parts are
brought to lower speeds.
❖ Hence they are suitable only for low speed
applications. And they also tend to get damaged
quickly as compared to the friction clutches.

FRICTION CLUTCH:
Clutch Disengaged Clutch Engaged

1. SINGLE PLATE CLUTCH
Construction:
❖ A single plate friction clutch consisting of a single
clutch disk between the flywheel and a pressure
plate.
❖ Both the pressure plate and the flywheel rotates with
the engine crankshaft or the driving shaft.
❖ And both sides of clutch disc are faced with friction
material.
❖ The clutch disc is mounted on the hub which is free
to move axially along the splines of the driven shaft
but not turnable towards the transmission input shaft.

Construction (contd..):
❖ The pressure plate pushes the clutch plate towards the
flywheel by a set of strong springs which are arranged radially
inside the body.
❖ The three levers (also known as release levers or fingers) are
carried on pivots suspended from the case of the body.
❖ These are arranged in such a manner so that the pressure
plate moves away from the flywheel by the inward movement
of a thrust bearing.
❖ The bearing is mounted upon a forked shaft and moves
forward when the clutch pedal is pressed.

WORKING:
Disengaging the clutch:
 By pressing the clutch pedal down, the thrust bearing moves
towards the flywheel by means of linkage force, and press the
longer end of the lever inwards.
 The lever turns on their suspended pivot and forces the pressure
plate to move away from the flywheel this action compresses the
clutch springs which in turn moves the pressure plate away from
the clutch plate and remove the pressure from the clutch plate.
 This enables the clutch plate to move back from the flywheel and
thus, the driven shaft becomes stationary.
Engaging the clutch:
 By moving the foot back from the clutch pedal, the thrust bearing
moves back and allows the spring to extend which pushes the clutch
plate backwards the flywheel.
 This engages the flywheel and the clutch plate which starts the
motion of the driven shaft.

2. MULTIPLATE CLUTCH
Construction & Working:
➢ Multiplate clutch consists of a number of clutch plates,
➢ As the number of clutch plates are increased, the friction
surface also increase.
➢ Increases the capacity of the clutch to transmit torque
in automobiles.
➢ The plates are alternately fitted to the engine shaft and
gear box shaft. They are firmly pressed by strong coil springs
and assembled.

CONSTRUCTION & WORKING(CONTD…)
 Each of the alternate plate slides in grooves on the flywheel
and the other slides on splines on the pressure plate.
Therefore, each alternate plate has inner and outer splines.
 The multiplate clutches operating condition may be dry or
wet.
 When the clutch is operated in an oil bath, it is called a
wet clutch.
 When the clutch is operated dry, it is called dry clutch. The
wet clutches are generally used.
 Multiplate clutch works in the same way as the single plate
clutch.

APPLICATIONS:
The multiplate clutches are used in
➢ Heavy commercial vehicles,
➢ Automobiles,
➢ Racing cars and
➢ Motor cycles for transmitting high torque.

3.CONE CLUTCH
Construction & Working:
 A friction type clutch, Simple in construction and are easy to
engage and disengage.
 The driving and driven shafts must be perfectly coaxial for
efficient functioning of the clutch.
 Friction surfaces in the form of cone.
 The engine shaft consists of a female cone, the male cone can
slide on the clutch shaft.
 When the clutch is engaged the friction surfaces of the male cone
are in contact with that of the female cone due to the force of spring.
 When the clutch pedal is pressed, the male cone slides against
the spring force and the clutch is disengaged.

 A contact lever is used to disengage the clutch.
 The inner cone surface is lined with friction material.
 Due to wedging action between the conical working
surfaces, there is considerable normal pressure and friction
force with a small engaging force.
 The semi cone angle a is kept greater than a certain
value to avoid self-engagement; otherwise disengagement of
clutch would be difficult. This is kept around 12.50.
Cont…

4. CENTRIFUGAL CLUTCHES
 The centrifugal clutch permits the drive motor to start,
warm up and accelerate to the operating speed without
load.
 Then the clutch is automatically engaged and the driven
equipment is smoothly brought up to the operating speed.
 These clutches are highly useful for heavy loads (large
machines) where the motor cannot be started under that
load.

CONSTRUCTION :
 The centrifugal clutch works on the principle of centrifugal force,
which increases proportional to the square of rotational speed.
 Guides or spiders are mounted on the driver or motor shaft.
 They are equally spaced such that if there are four guides, they are
separated by 90º.
 Sliding shoes are placed between the guides and each is retained
by a spring.
 The outer surface of the sliding shoe is provided with a lining of
friction material.
 A co-axial drum, which is mounted on the output or driven shaft,
encloses the assembly of spider, shoes and spring.

WORKING:
 When the motor is started, the rotational speed of
input shaft increases, and hence the centrifugal force
acting on the sliding shoe increases.
 This causes each shoe to move outward.
 The shoe continues to move with increasing speed
until they contact the inner surface of drum,
overcoming the spring force.
 Torque is transmitted due to frictional force between
the shoe lining and the inner surface of drum

OTHER APPLICATIONS OF CENTRIFUGAL CLUTCHES:
 Centrifugal clutch is widely used in textile
machinery such as looms, carding, knitting, drawing,
roving and spinning machines.
Advantages:
 Centrifugal clutch is economical, requires less
maintenance and safe (motor safety) compared to
any other device coupling.

Unit-3-Transmission system of Automobile

More Related Content

What's hot (20)

Similar to Unit-3-Transmission system of Automobile (20)

More from Dr.S.SURESH (18)

Recently uploaded (20)

Unit-3-Transmission system of Automobile