How a Rear differential works in a vehicle?

Rear differential


rear differential gears, rear axle differential.
Rear differential

If a car travels in a straight line, the two rear wheels turn on the road exactly at the same speed. There is no relative movement between the two rear wheels. The propeller shaft may be geared rigidly, in this case, the rear Axle to rotate the rear wheels together.
rear differential gears, rear axle differential.
Rear differential

But when the car takes a turn the outer wheels travel a longer radius than the inner wheel. The outer wheels turn faster than the inner wheel, that is, there is a relative movement between the two rear wheels. If two rear wheels are rigidly fixed to the rear axle the inner wheel will slip, which will cause rapid Tyre wear, steering difficulties, and poor road holding. Therefore there must be some device to provide relative movement to the two rear wheels when the car is taking a turn. The rear differential serves this purpose.

 
The rear differential is a part of the inner axle housing assembly, which includes the Rear differential, rear axle assembly, wheels, and bearings. The rear differential consists of a system of gears arranged in such a way that connects the propeller shaft with the rear axle. The torque transmitted two each wheel is however equal.

Construction:

Below figure shows the construction of a simple rear differential. The sun gears are mounted on the inner end of each rear axle (called half shaft). A Rear differential cage is assembled on the left axle. A ring gear (called crown gear) is attached to the case, so the cage rotates with the crown gear. The crown gear is driven by the bevel pinion. Both the crown wheel and cage are free on the left rear axle. The cage supports two planet pinions on a shaft which mesh with the two sun gears.
 

rear differential gears, rear axle differential.
Rear differential

When the Rear differential cage is rotated, both the sun gears rotate and thus, both wheels turn which is attached to the outer end of the rear axles. Now let us suppose that one wheel is held stationary. Then when the rear differential cage is rotated, the planet gears will also rotate it as they run around on the stationary axle sun gear. While rotating in this manner, the planet pinions carry a rotary motion to the other axle sun gear, causing it, and the wheel too, to rotate. Therefore when one wheel turns more rapidly than the other, while the car is taking a turn, the planet gears spin on its shaft transmitting more rotary motion to one rear wheel than to the other. When both the rear wheels Turn at the same speed the planet pinions do not rotate on the shaft. Thus, when the car is running in a straight line, the Crown wheel, rear differential cage, planet Pinions and the sun gear all turns as a unit without any relative motion. But when the car takes a turn, the planet pinions rotate on their shaft to permit the outer rear wheel to turn more rapidly than the inner Wheel.

Also Read:

  1. Locking differential.
  2. Limited Slip Differential.
  3. what is epicyclic differential?
  4. Hypoid differential.
  5. Applications of Center differential with a mechanical lock.
To understand the working concept of the rear differential, please watch the video below.


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