AUTOMOBILE DIFFERENTIAL UNIT

BY M KAUTAM PRASANT(O815121)

S RAJIV KUMAR(0815140)SAI PRASHANT K (0815146)

DIFFERENTIAL

• A differential is a device, usually employing gears• It is capable of transmitting torque and rotation

through three shafts.• It is always used in one of two ways: In one way, it receives one input and provides

two outputs (this is found in most automobiles) In the other way, it combines two inputs to

create an output that is the sum, difference, or average, of the inputs.

• The differential unit is helpful in transmitting the power generated from the crank shaft

• In case of two wheel drive, it transmits the power to the set of wheels thus causing uniform motion

• In case of all wheel drive, it transmits the power to all the wheels employing two units of differential.

TYPES OF DIFFERENTIAL

• Positive traction differential• Limited slip differential• Air Locking differential• Automatic Torque biasing differential• High frictional ZF differential• Torsen differential(Tourque Sensing)

AIR LOCKING DIFFERENTIAL

TYPES OF GEARS USED IN DIFFERENTIAL

• Bevel Gears• Helical Gears• Spur Gears

SECTIONS IN A DIFFERENTIAL

SIGNIFICANCE OF DIFFERENTIAL• Motion of vehicle in straight path• Motion of vehicle in curved path(Turnings)• Travelling in uneven roads

DIFFERENTIALS IN FWD RWD AND AWD

PRINCIPLE OF OPERATIONDURING STRAIGHT PATH

• Input torque is applied to the ring gear (blue), which turns the entire carrier (blue).

• The carrier is connected to both the side gears (red and yellow) only through the planet gear (green).

• Torque is transmitted to the side gears through the planet gear.

• The planet gear revolves around the axis of the carrier, driving the side gears.

• If the resistance at both wheels is equal, the planet gear revolves without spinning about its own axis, and both wheels turn at the same rate.

DURING A TURN

IN ADDITION, DURING TURNING• If the left side gear (red) encounters

resistance, the planet gear (green) spins as well as revolving, allowing the left side gear to slow down, with an equal speeding up of the right side gear (yellow).

OPEN LOCK DIFFERENTIAL

• One undesirable side effect of a conventional differential is that it can limit traction under less than ideal conditions.

• To over come such problems, open differentials(non-locked, traction aided) are used.

• A conventional open differential can limit torque applied to the driving wheels

OPERATION OF OPEN DIFFERENTIAL

DIFFERENTIALS AND TRACTION

• The open differential always applies the same amount of torque to each wheel.

• Two factors that determine how much torque can be applied to the wheels: equipment and traction.

• In dry conditions, when there is plenty of traction, the amount of torque applied to the wheels is limited by the engine and gearing

• In a low traction situation, such as when driving on ice, the amount of torque is limited to the greatest amount that will not cause a wheel to slip under those conditions.

• Even though a car may be able to produce more torque, there needs to be enough traction to transmit that torque to the ground.

• If you give the car more gas after the wheels start to slip, the wheels will just spin faster.

• Hence to over come this slippery surface problems or off-road stuck problems, we use

• Limited slip differential (LSD), sometimes called positraction.

• When a wheel slips, they allow more torque to be transferred to the non-slipping wheel

CLUTCH TYPE LIMITED SLIP DIFFERENTIAL

• The clutch-type LSD is probably the most common version of the limited slip differential.

• This type of LSD has all of the same components as an open differential, but it adds a spring pack and a set of clutches.

• Some of these have a cone clutch that is just like the synchronizers in a manual transmission.

• The spring pack pushes the side gears against the clutches, which are attached to the cage.

• Both side gears spin with the cage when both wheels are moving at the same speed, and the clutches aren't really needed -- the only time the clutches step in is when something happens to make one wheel spin faster than the other, as in a turn.

• If one wheel wants to spin faster than the other, it must first overpower the clutch.

• The stiffness of the springs combined with the friction of the clutch determine how much torque it takes to over power it.

• With this limited slip differential, even though the wheel on the ice is not able to transmit much torque to the ground, the other wheel will still get the torque it needs to move.

• The torque supplied to the wheel not on the ice is equal to the amount of torque it takes to overpower the clutches.

• The result is that you can move forward, although still not with the full power of your car.

THANK YOU