detailed matter for heart of automobile

1. PRESENTED BY :
C.JAIPAL REDDY
U14ME150
MECHNICAL DEPARTMENT
III YEAR ‘B’ SECTION
GEARBOX
SYSTEM

2. What is Gearbox?
 An automobile requires high torque when climbing hills and when
starting, even though they are performed at low speeds.
 On other hand, when running at high speeds on level roads,
high torque is not required because of momentum. So
requirement of a device is occur, which can change the vehicle’s
torque and its speed according to road condition or when the
driver need.
 This device is known as transmission box.

3. Introduction to Gearbox
 Gearbox often referred as transmission is a unit that uses gears and gear
trains to provide speed and torque conversions from a rotating power
source to another device. Gearboxes are employed to convert input from
a high speed power sources to low speed(E.g. Lift, Cranes
and Crushing Machine) or into a many of speeds(Lathe, Milling Machine
and Automobiles).
 A gearbox that converts a high speed input into a single output it is called
a single stage gearbox. It usually usually has two gears and shafts.
 A gearbox that converts a high speed input into a number of different
speed output it is called a multi-speed gear box. Multi speed gear box has
more than two gears and shafts. A multi speed gearbox reduces the
speed in different stages.

4. Main components of a gear
box
 In any device two or more component works
together and fulfills the required function. In a
transmission box four components are required to
fulfill its function.
 Counter shaft
 Main shaft
 Gears
 Bearings

5. components
1. Counter shaft:
 Counter shaft is a shaft which connects with the clutch shaft directly. It contains the gear which
connects it to the clutch shaft as well as the main shaft. It may be run runs at the engine speed or at
lower than engine speed according to gear ratio.
2. Main shaft:
 It is the shaft which runs at the vehicle speed. It carries power form the counter shaft by use of gears
and according to the gear ratio, it runs at different speed and torque compares to counter shaft. One
end of this shaft is connects with the universal shaft.
3. Gears:
 Gears are used to transmit the power form one shaft to another. They are most useful component of
transmission box because the variation is torque The gear ratio is the ratio of the driven gear teeth to
the driving gear teeth. If gear ratio is large than one, the main shaft revolves at lower speed than the
counter shaft and the torque of the main shaft is higher than the counter shaft. On other hand if the
gear ratio is less than one, than the main shaft revolves at higher speed than the counter shaft and
the torque of the main shaft is lower than the counter shaft. A small car gear box contains four speed
gear ratio and one reverse gear ratio.
4. Bearings:
 Whenever the rotary motion, bearings are required to support the revolving part and reduce the
friction. In the gear box both counter and main shaft are supported by the bearing.
 of counter shaft and main shaft is depend on the gear ratio.

6. Working of a principle gear box
 In a gear box, the counter shaft is mashed to the clutch with a use of
a couple of gear. So the counter shaft is always in running condition.
When the counter shaft is bring in contact with the main shaft by use
of meshing gears, the main shaft start to rotate according to the gear
ratio.
 When want to change the gear ratio, simply press the clutch pedal
which disconnect the counter shaft with engine and change connect
the main shaft with counter shaft by another gear ratio by use of
gearshift lever.
 In an gear box, the gear teeth and other moving metal must not
touch. They must be continuously separated by a thin film of
lubricant. This prevents excessive wear and early failure. Therefor a
gearbox runs partially filled with lubricant oil.

7. Gear teeth
 Depending on the size of the vehicles, the
size of the gears also varies. There are
low gears covering a shorter distance and
are useful when speed is low. There are
high gears also with larger number of
teeth.

8. Functions of Transmission
 To provide the high torque at the time of starting, hill climbing,
accelerating and pulling a load since high tractive effort is needed
 It permits engine crankshaft to revolve at high speed, while the
wheels turn at slower speeds
 Variable torque by set of gears
 Vehicle speed can be changed keeping engine speed same with
certain limit
 The transmission also provides a neutral position so that the engine
and the road wheels are disconnected even with the clutch in the
engaged position
 A means to back the car by reversing the direction of rotation of the
drive is also provided by the transmission

9. Type of gearbox
Generally following gearboxes are used in industries:
 Helical gearbox
 Bevel-helical gearbox
 Worm gearbox
 Heli-worm gearbox
 Geared motor

10. Types of Gearboxes
Types of Gearboxes:
 Sliding Mesh Gear box
 Constant Mesh Gear Box
 Synchromesh Gear Box
 Epicyclic Gear Box
An engine may consist of one or more gearbox.
There may be gearboxes which are a mixture of these types.

11. Sliding Mesh Gearbox
 In this type of gear box, gears are engaged and disengaged by sliding of the
gear wheels.
 Gear wheels on the main shaft engage with gear wheels on the lay shaft or
counter shaft by sliding themselves.
1.main drive gear
2.counter shaft
3.main shaft
4.I gear
5.II gear
6.III gear
7.top speed engaging
dogs

12. Constant Mesh Gearbox
 In this case, gear wheels on the main shaft and lay shafts are
constantly engaged and the rotary motion is transmitted to the
main shaft by engaging dog clutches.
1.I speed gear
2.II speed gear
3.main shaft
4.III speed gear
5.top and III speed engaging
dogs
6.top gear
7.primary shaft or main drive
gear
8.counter shaft/cluster gear

13. Constant Mesh Gearbox
Advantages of Constant mesh gearbox over Sliding mesh Gearbox:
 Helical and herringbone gear can be employed in these gearboxes and,
therefore, constant mesh gearboxes are quieter.
 Since the gears are engaged by dog clutches, if any damage occurs while
engaging the gears, the dog unit members get damaged and not the gear
wheels.
 By suitably designing the dog clutch, the gear changing can be made
easier.
 Damage to the dog clutch is less likely because all the teeth are engaged at
a time.

14. Synchromesh Gearbox
 If the car is moving, the output shaft is always turning (because ultimately it
is connected to the wheels).
 The layshaft is usually connected to the engine, but it is free-spinning once
the clutch has been operated.
 Because the gears are meshed all the time, the synchro brings the layshaft
to the right speed for the dog gear to mesh.
 This means that the layshaft is now spinning at a different speed to the
engine, the clutch gently equalises the speed of the engine and the layshaft,
either bringing the engine to the same speed as the layshaft or vice versa
depending on engine torque and vehicle speed.

15. Synchromesh Gearbox
 The green cone-shaped
area is the syncho collar.
It's attached to the red dog
gear and slides with it.
 As it approaches the helical
gear, it makes friction
contact with the conical
hole.
 The more contact it makes,
the more the speed of the
output shaft and free-
spinning helical gear are
equalized before the teeth
engage.

16. Epicyclic Gearbox
 In such gear boxes epicyclic
gear trains are employed to
get the various gear ratios.
 The characteristic feature of
an epicyclic gearing is that at
least one wheel not only
rotates about its own axis but
also rotates about some other
axis.

17. Epicyclic Gearbox
Automatic gearboxes
typically use one or more
compound planetary gear
sets instead of chaining
regular gear sets
together.
They look just like a
regular planetary gear set
from the outside, but
inside there are two sun
gears and two sets of
intermeshing planet
gears.
There is still only one
ring gear though.

18. Epicyclic Gearbox

19. Types of Transmissions
Common Types include:
 Manual Transmission
 Semi-Automatic Transmission
 Automatic Transmission
Uncommon Types include:
 Dual clutch transmission
 Continuously Variable Transmission [CVT]
 Infinitely Variable Transmission [IVT]
 Electric Variable Transmission [EVT]
 Hydrostatic
 Hydrodynamic
 Electric

20. Manual Transmission

21. Semi-Automatic Transmission

22. Automatic Transmission
 Epicyclic Gearing or Planetary Gearing are
as used in an automatic transmission. An
Automatic transmission will select an appropriate
gear ratio without any operator intervention.
They primarily use hydraulics to select gears,
depending on pressure exerted by fluid within
the transmission assembly.

23. Automatic Transmission
Cutaway view of a typical 3-speed automatic transmission

24. Advantages
Here are some of the features of an automatic
transmission:
 If the car is in overdrive (on a four-speed transmission),
the transmission will automatically select the gear based
on vehicle speed and throttle pedal position.
 If you accelerate gently, shifts will occur at lower speeds
than if you accelerate at full throttle.
 If you floor the gas pedal, the transmission will downshift
to the next lower gear.

25. Disadvantages
Disadvantages of Automatic Transmission over Manual
Transmission:
 Its mechanical efficiency is very less than that of a manual
transmission type.
 Its requires a specialized transmission fluid/lubricants which
is expensive and need to be changed regularly.
 Its expensive to manufacture.
 It is heavier than an conventional manual transmission
gearbox.
 It has much higher rate of failure due to complexity.

26. Thank You