A differential is a mechanical component of a vehicle's drivetrain.
When a car turns, the outer wheels travel a greater distance than the inner wheels. Therefore, for a car to turn smoothly and accurately, a device is needed that can allow the inner and outer wheels to rotate at different speeds, thus compensating for the difference in distance traveled.
Structure and principle
Both the red and yellow shafts have resistance, and the planetary gears do not move.
A typical differential uses a planetary gear mechanism, which includes two planetary gears and two half-shaft gears connected to the drive shafts. These four gears are housed within an internal casing of the differential and mesh with each other. Each gear meshes with two other gears (each half-shaft gear meshes with two planetary gears, and each planetary gear meshes with two half-shaft gears). Therefore, if one gear rotates, it will inevitably cause the other three gears to rotate as well. When one half-shaft gear rotates in a certain direction, the other half-shaft gear will inevitably rotate in the opposite direction. This phenomenon can be demonstrated experimentally: when both drive wheels of a vehicle are suspended, rotating one wheel in one direction will inevitably cause the other wheel to rotate in the opposite direction.左边卡住
The planetary gears begin to rotate.
When the car is driving in a straight line, the resistance on the left and right drive wheels is approximately the same. The output shaft of the engine (i.e., the input shaft of the differential) drives the half-shaft gears on both sides. Since the resistance on both sides is equal, the two planetary gears in the middle rotate along with the half-shaft gears without rotating on their own axis. When the vehicle turns, one side's wheel travels a shorter distance than the other, resulting in greater resistance on that side. This means that the planetary gears have to work harder to rotate the wheel on that side. This balance is disrupted, forcing the planetary gears to rotate on their own axis, increasing the speed of the outer wheel and allowing the vehicle to turn smoothly.
The South-Pointing Chariot, an ancient Chinese application of differential gear technology.
Disadvantages:
Because the differential allows the wheels on both sides to rotate at different speeds, when one of the vehicle's drive wheels slips, or when one wheel lifts off the ground due to aggressive driving, the equal torque distribution of the differential causes all the power to be transmitted to the slipping half-shaft, making the slipping wheel spin rapidly while the other wheel loses driving force (see Figure 2 on the right). This can cause the vehicle to become stuck and lose controllability.
Although the differential solves the problem of difficulty in turning, for vehicles with off-road or competitive driving requirements, the inability to limit slippage reduces the vehicle's off-road capability and handling. Therefore, limited-slip differentials and differential locks are needed to meet the demands of vehicle racing and off-road driving. Internal structure diagram
