Differential-final-drive-system (1).pptx

diffrential system it is a part of power transmission system in tractor and also other vehical

1. Working principle of differential system and final drive Presented b y GEETA PATEL

2. Differential unit is a special arrangement of gears to permit one of the rear wheels of the tractor to rotate slower or faster than the other. While turning the tractor on a curved path, the inner wheel has to travel lesser the tractor to move faster than the other at the turning point. Differential unit

3. The output shaft coming from the gear box is provided with a bevel pinion at the end of the shaft. The bevel pinion is in mesh with a large bevel wheel known as crown wheel. The main functions of crown wheel assembly are: (i) to transmit power through right angle drive to suit the tractor wheels. (ii) to reduce the speed of rotation .

4. Main Functions o f Differential Further reduces the rotations coming from the gear box before the same are passed on to the rear axles. Changes the direction of axis of rotation of the power by 90 degree i.e. from being longitudinal to transverse direction. To distribute power equally to both the rear driving axles when the tractor is moving in straight ahead direction. To distribute the power as per requirement to the driving axles during turning i.e. more rotations are required by the outer wheel as compared to the inner wheel – during turns.

5. The main components of the differential are : Input pinion gear Crown wheel gear Differential cage Differential star Differential axle (sun) gear

6. W ORKING The differential casing is rigidly attached with the crown wheel and moves like one unit. Two pinions are provided inside the differential casing, such that they are carried round by the crown wheel but they are free to rotate also on their own shaft or stud. There are two or more bevel gears in mesh with differential pinion . One bevel pinion is at the end of each half shaft, which goes to the tractor rear wheel

7. Thus instead of crown wheel being keyed directly to a solid shaft between the tractor wheels, the drive is taken back from the indirect route through differential casing, differential pinion and half shaft of the tractor When the tractor is moving in a straight line, the differential pinion do not rotate on the stub shaft but are solid with the differential casing. They drive the two bevel gears at the same speed and in the same direction as the casing and the crown wheel .

8. Differential lock: Differential lock is a device to join both half axles of the tractor so that even if one wheel is under less resistance, the tractor comes out from the mud etc as both wheels move with the same speed and apply equal traction .

9. FINAL DRIVE Final drive is a gear reduction unit in the power trains between the differential and the drive wheels. Final drive transmits the power finally to the rear axle and the wheels. The tractor rear wheels are not directly attached to the half shafts but the drive is taken through a pair of spur gears. Each half shaft terminates in a small gear, which meshes with a large gear called bull gear. The bull gear is mounted on the shaft, carrying the tractor rear wheel. The device for final speed reduction, suitable for tractor rear wheels is known as final drive mechanism .

10. Types of final drive Bull gear type Hub reduction axles Straight axle Planetary Ring Gear The ring gear is a large circular gear that forms the outer part of the final drive assembly . It is connected to the differential unit or planetary gear set and rotates with the movement of the tractor's wheels. The ring gear engages with other gears in the final drive, transferring power and torque to the wheels. Pinion Gear The pinion gear is a small gear that meshes with the ring gear . It is connected to the tractor's transmission output shaft or axle shaft and rotates with the transmission's input speed. As the pinion gear engages with the ring gear, it transmits the rotational force to the final drive, thereby turning the tractor's wheels .

11. The bull gear final drive system consists of a set of gears and shafts that transmit power from the tractor's transmission to the rear wheels. The gears are called bull gears, which mesh with small pinions attached to the axle shafts. This system provides high torque and power to the wheels, making it suitable for heavy-duty applications. Bull gear final drives are commonly found in larger and older tractors.

12. Hub reduction axles employ a planetary gear system within the wheel hub to enhance torque and load-carrying capacity. These axles reduce rotational speed while significantly increasing torque, crucial for heavy-duty tasks like pulling or carrying substantial loads. They bolster the off-road capabilities of a tractor to improve the traction in challenging terrains. Additionally, they distribute the load among multiple components, reducing axle stress and enhancing longevity.

13. A straight axle, also known as a solid axle or live axle, is a common type of axle used in many tractors and other heavy-duty vehicles. It offers simplicity, durability, load distribution, and excellent traction, making it suitable for heavy-duty agricultural tasks and off-road operations. Tractors with straight axles typically employ other mechanisms for steering while relying on the solid axle for load bearing and stability.

14. The planetary final drive system utilises a set of planetary gears to transmit power from the transmission to the wheels. These gears are compact and provide a higher gear reduction. It results in increased torque and traction. Planetary final drives offer better manoeuvrability. It makes them ideal for smaller tractors and those used in agricultural applications. Planetary rear axle is also known as epicyclic reduction.

15. Power Transmission : It transfers power from the tractor's transmission to the wheels. It ensures efficient power delivery, enabling the tractor to move with the required torque and speed. Gear Reduction : It helps convert the high-speed, low-torque output from the transmission into the necessary low-speed, high-torque output at the wheels. As a result, tractor generates more pulling power to handle heavy loads. Speed Control : It alters the gear ratios within the final drive to help the operator adjust the speed at which the tractor moves ensuring precise control and operation in various conditions. Direction Control : It engages different drive shafts and gears to help the operator determine the direction the tractor moves, whether forward, reverse, or turning. Traction : Good traction is essential for preventing slippage and ensuring efficient operation, particularly in challenging terrain. Torque Multiplication : In the case of planetary final drives, they offer torque multiplication, which is crucial for tasks that require significant pulling or pushing force, such as tilling or pulling heavy loads . Functions of the Final Drive in Tractors

16. P R OBLEM