When the car turns, the wheels spin at different speeds. In the animation below, you can see that when turning, the distance traveled by each wheel is not equal, that is, the distance traveled by the inner wheel is shorter than the distance traveled by the outer wheel. Because the speed of the car is equal to the distance traveled by the car divided by the time it takes to pass this distance, wheels with a short distance travelled at a slower speed. At the same time, it should be noted that the distance covered by the front wheel is different from that of the rear wheel. For the driven wheels of rear-wheel drive vehicles or the driven wheels of front-wheel drive vehicles, there is no such problem. Since they are not connected to each other, they rotate independently of each other. But the two driving wheels are related to each other. Therefore, one engine or one gearbox can drive two wheels at the same time. If you don’t have a differential in your car, the two wheels will have to be fixedly coupled together and driven to rotate at the same speed. This can cause difficulty in steering the car. At this point, in order for the car to turn, one tire will have to slip. For modern tires and concrete roads, it takes a lot of external force to make the tire slip. This force is transmitted from one tire to another through the axle, which causes great stress on the axle components.
What is a differential
The differential is a device that divides the output torque of the engine into two, allowing two different speeds to be output when steering.
Differentials can be found in modern cars or trucks, including many four-wheel drive cars. These four-wheel drive vehicles require a differential between each set of wheels. Similarly, a differential is required between the two front wheels and the two rear wheels. This is because when a car turns, the distance traveled by the front wheels is different than that of the rear wheels. Some four-wheel drive vehicles do not have a differential between the front and rear wheels. Instead, they are fixedly connected so that the front and rear wheels can turn at the same average speed when turning. This is why this type of vehicle has difficulty steering when the four-wheel drive system is busy. Turning at different speeds, we will start with the simplest type of differential-the open differential. First of all, we need to understand some technologies: the picture below is an open differential component. When a car is driving straight along a road, the wheels on both sides rotate at the same speed. The input pinion drives the spiral bevel gear and the housing. The pinion gears in the housing do not rotate, and the teeth on both sides effectively lock the housing. Note that the gear of the input pinion is smaller than that of the spiral bevel gear. If the final reduction ratio is 4.10, the number of teeth of the spiral bevel gear will be 4.10 times more than that of the input pinion. For more information about the transmission rate, please refer to How Gears Work. When a car turns, the wheels must spin at different speeds. From the picture above, you can see that the pinion in the housing starts to rotate when the vehicle is turning. In this way, the wheels on both sides rotate at different speeds. The inner wheel turns slower than the shell. But the outer wheels have to turn relatively fast.