Why differential is used in automobile
Need of Differential in automobile:
1) When vehicle is taking turn outer wheel will have to travel greater distance as
compared to inner wheel.
2). If the vehicle has a solid rear axle only and no other device, there will be
tendency to skid.
3. Hence wheel skidding is avoided by incorporating the mechanism i.e.
differential.
4) Differential reduces the speed of inner wheel and increases the speed of outer
wheel when vehicle is taking turn, at the same time keep the speed of rear wheel
same when going straight ahead.
Working of Differential :
1. When vehicle moves in a straight line:
The power comes from propeller shaft to the bevel pinion which drives the crown
wheel. Then it is carried to the differential cage in which a set of planet pinions and
sun gears are located. From the sun gear it is transmitted to the road wheels through
axle half shafts. In this case, the crown wheel, differential cage, planet pinions and
sun gears all turn as a single unit and there is no any relative motion between the
sun gear and planet pinion. The planet pinions do not rotate about their own axis.
The road wheels, half shafts and sun wheels offer the same resistance to being
turned and the differential gearing does not therefore operate. Both the road wheels
turn at the same speed.
2. When Vehicle takes a turn:
The inner wheel experiences a resistance and tends to rotate in opposite direction.
Due to this the planet pinions starts rotating about their own axis and around the
sun gear and transmit more rotary motion to the outer side sun gear. So that outer
sun gear rotates faster than the inner sun gear. Therefore the outer road wheel runs
faster than the inner road wheel and covers a more distance to negotiate a turn
safely.
