Introduction to differential gearbox:

Differential Gearbox: Definition, Type, Components, Function, Materials, Principles, Workflow, and Advantages: A differential gear is a set of gears that transmit engine power to the wheels while causing them to rotate at different speeds. In rear wheel drive, the differential is located between the rear wheels, which are associated or connected to the transmission through the drive shaft. When the vehicle is driving in a straight line, the differential will not have any impact. When a vehicle attempts to turn, it can have an impact, causing the wheels to move at different speeds.

What is a gearbox?

A gearbox is a component that provides torque to change or alter the engine speed. One end of the input shaft is connected to the engine, and the other end is connected to the gearbox. The output shaft provides specific torque or force given by different gear ratios in the gearbox.

What is a differential gearbox?

A differential gearbox is one of the fundamental components of any car. If we talk about it according to automotive mechanics, a differential gearbox is a gear device that allows the engine's power to be transmitted to multiple drive wheels, evenly distributing force between them while allowing them to follow paths of different lengths, such as when turning or driving on rough roads. Gearboxes are used in almost all industries from electricity to ships, including agriculture, automobiles, aviation, shipping, and more.

There are various types of gearboxes that can be used for different purposes. These gearboxes are made of different materials, depending on their ultimate use and the type of industry they are applied to. This product has multiple industrial applications and can provide high torque and smooth deceleration. These gearboxes are also manufactured according to specific specifications, which will vary depending on the application.

Different types of differentials

Conventional type.

Anti slip or self-locking type.

Double deceleration type.

1. Conventional type

The traditional differential provides the same torque to each rear wheel. If any wheel slips for any reason, the wheel will not rotate and the vehicle will not move.

2. Anti slip or self-locking type

Anti slip or self-locking differential overcomes this drawback. Its structure is similar to that of a traditional differential. Nevertheless, two additional sets of clutch plates are provided. Similarly, the closure of planetary axis cages.

3. Double deceleration type

The double or double differential further reduces speed through additional gears. This differential is used for heavy-duty vehicles, which require larger gear reducers to be installed between the wheels and the engine.

The purpose of differential gearbox

When a vehicle turns on a curve, the outer wheel should travel a longer distance than the inner wheel. Assuming the rear axle of the vehicle is sturdy and there are almost no special devices, the likelihood of wheel slippage is higher. To avoid this situation, a device must be installed to reduce the speed of the inner wheel and increase the speed of the outer wheel, so that the speeds of the two wheels match each other, just like a vehicle traveling in a straight line. This device is called a differential. The differential gear supports two wheels.

To prevent tire wear, differential gears are always chosen to rotate at different speeds.

Compared to the outer wheel, the inner wheel rotates a smaller distance.

Function of differential gearbox

When a four-wheel drive turns, the outer wheel rotates faster than the inner wheel. Therefore, there is relative motion between the inner and outer wheels. Power is transmitted from the engine to the drive wheels. However, when turning, the two driving wheels do not require the same power, for example, when turning right, the outer wheel requires more power than the inner wheel. In addition to allowing the drive wheels to operate at different speeds, differential gearboxes are also used to reduce speed while transmitting torque.

The principle of differential gearbox

If the vehicle is traveling in a straight line, the rotational speed of the two rear wheels is precisely equivalent, and there is no relative motion between them. Anyway, when the vehicle turns, the outer wheel has a longer radius than the inner wheel, for example, there is relative motion between the two rear wheels. The outer wheel rotates faster than the inner wheel and travels a longer distance. The angle of the inner wheel is greater than that of the outer wheel. In this way, the vehicle can turn safely.

Why do we need a differential gearbox?

When the vehicle is driving in a straight line, the two rear wheels rotate at the same speed, and there is no relative motion between the two rear wheels. However, when the vehicle turns, the outer wheel has a larger driving radius than the inner wheel. The outer wheel rotates faster than the inner wheel, for example, there is relative motion between the two rear wheels.

If the two rear wheels are firmly fixed on the rear axle, the inner wheels will slip, resulting in rapid tire wear, difficult steering, and poor grip. Therefore, there should be some device to distribute the input torque of the transmission system between the two rear axles. The differential meets this requirement or purpose.

Materials used for differential gearbox

The gearbox is made of various materials. Here are some commonly used materials mentioned:

cast iron

aluminum alloy

steel

The transmission ratio of a bevel gearbox can be determined by dividing the number of teeth of the large gear by the number of teeth of the small gear. These gearboxes generate varying degrees of torque and can also be customized according to individual needs.

Components of differential gearbox

Drive small gears or bevel gears

Ring gear or crown wheel

Differential case

Differential side gear or sun gear

Differential small gear (or planetary gear)

Axle or half axle

Small gear shaft or cross pin

The following is a description of the basic components of differential types used in different vehicles:-

Each axle is equipped with a smaller bevel gear at the inner end, called the differential side gear. Two bevel gears are assembled together to operate the drive shaft and the driven shaft at a 90 ° angle. The two wheel axles and differential side gears are installed on the differential housing. The differential housing has a bearing that can rotate two half shafts. Then, at this point, the two small gears and their supporting shafts (referred to as the small gear shafts) are installed into the differential housing. Then, at this point, the small gear shaft meshes with the two differential side gears connected to the inner end of the half shaft.

If we talk about differential cases, the ring gear is fixed with dashed lines or bolts. The ring gear rotates the differential case. Finally, install the drive pinion. The drive pinion is collected together with the differential housing (known as the differential case). The drive shaft is connected or associated with the drive pinion through a universal joint and meshes with the ring gear. Therefore, when the drive shaft rotates, the drive pinion also rotates. In this way, the ring gear will rotate.

Where is the differential gearbox located?

In the front engine front wheel drive layout, the differential is located near the front of the gearbox.

In the rear engine rear wheel drive layout - in this case, the differential is located at the rear near the gearbox.

Four wheel drive layout - in this case, the differential is located at the front and rear

Front engine rear wheel drive layout - it is located between the two rear half axles.

The working process of differential gearbox

A) When driving straight

When power is transmitted from the propeller shaft to the helical gear that drives the crown wheel, it enables the vehicle to travel in a straight line. Then, there, power is transmitted to the differential housing, which contains a set of planetary gears and sun gears. From the sun gear, power is transmitted through the axle half shaft to the road or street wheels. In the current situation, the crown wheel, differential housing, planetary pinion, and sun gear all rotate as a unit, and there is no general motion between the sun gear and planetary pinion. The planetary pinion does not rotate around its own axis. The road wheels, half axles, and sun gear provide similar resistance when rotating, and the differential gear does not work. Two road wheels rotate at similar speeds.

B) When turning

When the vehicle feels free to move, the inner wheels will encounter resistance and rotate in the opposite direction as a whole. Therefore, the planetary pinion begins to rotate around its own axis and the sun gear, and transmits more rotational motion to the outer sun gear. The result is that the outer sun gear rotates faster than the inner sun gear. Therefore, the outer wheel runs faster and travels a longer distance than the inner wheel.

Advantages of differential gearbox

Due to the transmission of differential signals on balanced lines, they are safe or impenetrable to EM (electromagnetic) obstacles.

Differential gearbox helps to limit electronic crosstalk.

Two driving wheels can rotate in similar directions and at similar speeds.

Two driving wheels can rotate in the same direction at different speeds.

Two driving wheels can rotate in the other direction at similar speeds.

Two drive wheels can rotate in opposite directions at alternating speeds

When should the differential gearbox be replaced?

Transmission and differential faults usually do not occur accidentally. These transmission system components typically malfunction after a period of time, so identifying the root cause of these mechanical failures and repairing them before the vehicle becomes inoperable can save time and money.

The most common indicators indicating defects in the gearbox are as follows:-

When driving, error codes and warning lights will appear on the dashboard of the car.

The noise of collision or shaking is an early sign of gear shifting.

If there is a clicking or tapping sound, it indicates a defect in the gearbox.

The vehicle shakes when accelerating.

If you notice a strong burning smell around the gearbox, it indicates a defect in the gearbox and needs to be replaced.

The inability to locate the gear door may indicate a problem with the gearbox.

Conclusion

The differential is located in the center of the drive shaft, and its function is to ensure that the two wheels can rotate at different speeds and velocities while still having the same thrust when turning. The torque of the engine is always distributed in an appropriate proportion. Internal combustion engines operate at different power and torque levels. If there is no gearbox, the car will slow down from a stationary state or when the vehicle experiences a certain degree of resistance. Compared to the wheels, the engine actually runs at a higher speed.