Automotive drive system knowledge-differential

carEngine power experienceclutch,transmission,transmission shaftAnd finally sent toDrive axleAnd then assign left and right toHalf shaftDrive wheels. In this power transmission path, the drive axle is the last assembly, and its main components arereducerandDifferential. The function of the reducer is to decelerate and increase the torque. This function is completely completed by the meshing between the gears and the gears, which is relatively easy to understand. The differential is more difficult to understand, what is a differential, and why is it "differential"?

The car differential is the main part of driving the car.Its function is to transmit power to the two half-axes at the same time, allowing the two half-axes to be differentRotating speedRotate to meet the requirements of unequal-distance driving in the form of pure rolling as far as possible on both sides of the wheel, reducingtireFriction with the ground.

The trajectory of the wheel when the car turns is an arc. If the car turns to the left, the center point of the arc is on the left. In the same time, the arc on the right wheel is longer than the left wheel. In order to balance this difference , The wheel on the left should be slower and the wheel on the right should be faster. Different speeds are used to compensate for the difference in distance.

If the rear wheel axle is made as a whole, the speed difference of the wheels on both sides cannot be achieved, that is, automatic adjustment cannot be made. In order to solve this problem, as early as a hundred years ago, Louis Renault, the founder of the French Renault Automobile Company, designed the differential.

The ordinary differential is composed of planetary gears and planetary gear carriers (Differential case), half shaft gear and other parts. The power of the engine enters the differential through the transmission shaft and directly drives the planetary wheel carrier, and then the left and right half shafts are driven by the planetary wheels to drive the left and right wheels respectively. The design requirements of the differential should meet: (left half shaft speed) + (right half shaft speed) = 2 (planetary carrier speed). When the car is going straight, the rotational speeds of the left and right wheels and the planetary wheel carrier are equal and in a balanced state. When the car is turning, the balance of the three is broken, resulting in a decrease in the rotational speed of the inner wheel and an increase in the rotational speed of the outer wheel.

This adjustment is automatic, and it involves the "minimum energy consumption principle", that is, all objects on the earth tend to consume the least energy. For example, if you put a bean into a bowl, the bean will automatically stay at the bottom of the bowl and never on the wall of the bowl, because the bottom of the bowl is the position with the lowest energy (potential energy), and it automatically chooses to be static (minimum kinetic energy) instead of Will keep moving. In the same way, the wheels will automatically tend to the lowest energy consumption state when turning, and automatically adjust the speed of the left and right wheels according to the turning radius.

When turning, due to the slipping phenomenon of the outer wheel and the slipping phenomenon of the inner wheel, the two driving wheels will generate two additional forces in opposite directions at this time. Due to the "minimum energy consumption principle", it will inevitably lead to the wheels on both sides. The rotation speeds are different, which destroys the balance of the three, and is reflected on the half shaft gear through the half shaft, forcing the planetary gear to rotate, so that the outer half shaft speed is increased, and the inner half shaft speed is slowed down, thereby realizing the speed of the wheels on both sides. difference.