DIFFERENTIAL

Introduction:-

The differential is an integral part of all four wheeler. Differential technology was invented centuries ago and is considered to be one of the most
ingenious inventions human thinking has ever produced.The differential is a device that splits the engine torque two ways, allowing each output to spin at a different speed. 

Why the Differential gear is used?

Wheels receive power from the engine via a drive shaft. The wheels that receive power and make the vehicle move forward are called the drive wheels. The main function of the differential gear is to allow the drive wheels to turn at different rpms while both receiving power from the engine.

The differential has three jobs:

• To aim the engine power at the wheels
• To act as the final gear reduction in the vehicle, slowing the rotational speed of the transmission one final time before it hits the wheels
• To transmit the power to the wheels while allowing them to rotate at different speeds (This is the one that earned the differential its name.)

Parts of differential is shown in figure above :-

Differential Operation:-

Now let’s see how the differential manages to rotate the side gears (drive wheels) at different speeds as demanded by different driving scenarios.

The vehicle moves straight

In this case, the spider gear rotates along with the ring gear but does not rotate on its own axis. So the spider gear will push and make both the side gears turn, and both will turn at the same speed. In short, when the vehicle moves straight, the spider-side gear assembly will move as a single solid unit.

The vehicle takes a right turn

Now consider the case when the vehicle is taking a right turn. The spider gear plays a pivotal role in this case. Along with the rotation of the ring gear it rotates on its own axis. So, the spider gear is has a combined rotation. The effect of the combined rotation on the side gear is interesting.When properly meshed, the side gear has to have the same peripheral velocity as the spider gear. Technically speaking, both gears should have the same pitch line velocity. When the spider gear is spinning as well as rotating, peripheral velocity on the left side of spider gear is the sum of the spinning and rotational velocities. But on the right side, it is the difference of the two, since the spin velocity is in the opposite direction on this side.This means the left side gear will have higher speed compared to the right side gear. This is the way the differential manages to turn left and right wheels at different speeds.

The vehicle takes a left turn

While taking a left turn, the right wheel should rotate at a higher speed. By comparing with the previous case, it is clear that, if the spider gear spins in the opposite direction, the right side gear will have a higher speed.