Differantial (Mechanical Device)
The most important task for the vehicles not to fall over during rotation, to maintain their speed and to continue on their way is the differential. Cars are one of the fundamental technologies that have existed since our lives. The best example for you to understand this issue is that the outer side steps faster and the inner side slower in order not to disturb the order in the cortege executions. Let’s take a look at more technical details:
The differential, which is of great importance in bends, works simultaneously with both axles. It also allows the axles to rotate at different speeds. Because the two axles moving in the same way when cornering will endanger the rotation and even do not. While the cars are cornering, they follow a circular path and draw a spring. While doing this movement, the outer wheel draws a wider spring, while the inner wheel draws a smaller spring. It provides differential.
Located between both wheels, this part is connected by a half toothed shaft. On all-wheel drive vehicles, there are two separate differentials for each wheel pair. In this way, it ensures that all four wheels make an appropriate turn. After the rotational movement from the engine is transmitted to this part by the gearbox, the wheels are transmitted with the angle of rotation. The number of turns of the wheels is also regulated by the differential.
If there wasn’t this piece in a car; The power passing through the engine through the gearbox would be transferred directly and the wheels would spin at the same speed. The tires on the inside of the bend would wear out more quickly as the turns would overload. In addition, the wheels would not be able to turn to different speeds and road holding performance would deteriorate. As a result, safe driving would be compromised.
What is a Differential?
The differential is the part that allows two traction wheels to spin at different speeds. Because; When cars turn, the inner wheel should turn slightly slower than the outer wheel.
It is a gearbox that transmits the movement it receives from the gearbox to the axle shafts. The differential directs the rotating force from the gearbox, the torque, to the two axle shafts. In rear-wheel drive vehicles, this part breaks the movement 90 degrees and transmits it to the wheels. The part, which gives the right and left wheels the ability to rotate at different speeds, provides slippage and easy turning on bend and bumpy roads.
What is the Importance of Differential?
Since the car loses handling power when it is not differential, it is only a matter of time before the back of the car is blown away. Differential is very important for road holding safety. It was used for the first time in cars in 1916.
It is known to have been invented by Carlbens in the late 1800s. Since the concept of the car was not fully established in those years, its use in modern cars reaches 1916. Packard was the first person to use cars of that time differential.
What are the parts of the differential?
Differentials need 4 things, which we will count below, while performing these tasks. These;
Differential oils are an indispensable part of this system. When lubricating the system, special oils produced for differential must be used. These oils travel through the system thanks to the gears. There is also a bucket inside the differential, and this bucket has a total of 2 plugs, one above and below. The stopper on top is to fill the bucket with oil; the bottom plug is required to drain this oil.
It takes its name from an engineer named Schaft who invented him. Its task is to connect the gearbox and the differential, and keep the gearbox in the straight position at all times. The shaft is therefore designed flexibly. On uneven and hollow roads, the shaft keeps the gearbox constantly in the straight position by providing the inclinations and flexibility falling on it in the shaking of the car.
In order for us to understand better; we can use the hammock example. Imagine a hammock tied between two masts on a ship. No matter how much the storm comes, no matter how much the wave hits, the ropes on the ship and the ropes on which the hammock is tied, they swing to the right and left due to the jolt coming, the rope flexes back and forth. But the hammock itself always remains flat. We can say that this system is developed thousands of times, it is the formula used in the differential.
It literally means general connectivity. It connects the shaft to the transmission on the one hand and to the differential on the other. It must be on both ends of the shaft. If the shaft consists of two parts, not one, 3 universal joints are sufficient. It has to be flexible enough not to feel the bumps and holes on the road. Otherwise it won’t work
Fixed Speed Joints
The task of these joints is to give the effect of the return force given to the wheels from larger angles and more effectively. Because a constant force is going from the workhorse to the wheels through the engine. It is this force that turns the wheel.
Here, the task of constant velocity joints is to ensure that these forces going from the workhorses go faster and to minimize the time interval between both forces going. And at the same time, it is able to transmit this great force to the wheels in the most gentle way in order not to damage the car. Like a sharp vinegar cube, if this force is given too hard, the biggest damage will be the car.
Fixed velocity joints consist of 4 parts:
“Outside” in which grooves are drilled,
Generally, “balls” in the parts called sockets
“Inner Ball” with grooves on the outer surface in order to ensure the operation of the balls,
“Rubbers” placed to protect the bellows and parts from dirt and moisture.
How Does Differential Work?
The movement from the gearbox is transmitted to the mirror gear via the drive gear. The mirror gear is mounted on the differential body. With this gear cage, the single piece transmits the rotary motion to the gear cage. The movement is transferred to the cross gear, which is mounted on the gear cage. If this is done, it transmits the return movement to the axle gears. Axle gears are in one piece with axle shafts. With the rotation of the axle shaft, the movement is transmitted to the wheels.
At this stage, the most important task belongs to the spur gear running between the two axle gears. This gear movement transmits to the axle gears, allowing the two axle gears to rotate at different speeds. As a result, corners can be taken without skidding and wheels rolling. With this feature, the cross gear is a balancing gear.
Classical differentials always transmit the traction force they receive from the engine to an equal amount of right and left axle shafts. In addition, the differential transmits the rotational speed it receives from the engine to the wheels in different quantities. This part allows both wheels to rotate at different speeds. With this task it performs thanks to the spindle gear that works independently between both axle gears.
What are the Differential Types?
There are 3 different types of differential. Let’s take a look at the details of these varieties that are open, locked and limited slip:
It is the classic differential type. In this type, where both wheels can turn at different speeds; Torque from the engine is always sent equally to both axles. That is, the torque on the axle shaft of the right wheel is equal to that on the left axle shaft. The maximum torque that the wheels can transfer to the ground depends on the smallest friction force between the wheel and the ground.
Both wheels have to rotate at the same speed and always send the speed from the engine evenly to both axles. Therefore, both wheels have to turn at the same speed. The torque transmitted by the right and left wheels is not equal. The maximum torque value that can be transferred to the wheels depends on the greatest friction force between the wheel and the ground. It is generally used in off-road and heavy vehicles.
This type of deactivation is concerned. If it is not removed, high speeds cannot be reached and safe cornering cannot be achieved. The reason for this is that the speeds of the right and left wheels will always be equal. Accordingly, the tires will slip, road holding will decrease, the vehicle will be knocked out and the tires will wear out quickly. When the differential is locked, it is generally not allowed to exceed 35 to 40 km / h. Therefore, limited slip differential (LSD) is used in passenger cars.
Limited Slip Differential
Expressed as Limited Slip Differential or LSD, this type works like an open type, but is activated when the amount of rotation between the two wheels exceeds a certain value. In the meantime, it locks the two axle shafts and equalizes the speed. There are viscous, multi-disc and threaded types. It is the most used locked differential type in passenger cars.