What is a differential? What does it do?

The car differential is the main part that drives the car. Its function is to transmit power to both side half shafts at the same time, allow the two side half shafts to rotate at different speeds, meet the two sides of the wheel as far as possible in the form of pure rolling for unequal distance driving, reduce the friction between the tire and the ground.

If the car turns to the left, the center point of the arc is on the left, in the same time, the arc of the right wheel is longer than the left wheel, in order to balance this difference, the left wheel should be slower and the right wheel faster, and use different speeds to make up for the difference in distance.

If the rear axle is made as a whole, it is impossible to achieve the difference in the speed of the two wheels, that is, it cannot be automatically adjusted. In order to solve this problem, as early as a hundred years ago, Louis, the founder of the French company Renault. Renault came up with the differential.

Ordinary differentials are composed of planetary gears, planetary wheel carriers (differential housings), half-shaft gears, and other parts. The power of the engine enters the differential through the transmission shaft, directly drives the planetary wheel carrier, and then the planetary wheel drives the left and right half shafts to drive the left and right wheels respectively. The design requirements of the differential meet the requirements:

Left half shaft speed) + (right half shaft speed) = 2 (planetary wheel carrier speed). When the car goes straight, the rotation speed of the left and right wheels and the planetary wheel carrier is equal and in a balanced state, and the balance state of the three is destroyed when the car turns, resulting in the decrease of the rotation speed of the inner wheel and the increase of the rotation speed of the outer wheel.

This adjustment is automatic, and here it involves the "principle of minimum energy consumption", that is, all objects on the earth tend to be in a state where they consume the least energy. For example, if you put a bean in 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 lowest energy (potential energy), and it will automatically choose to be stationary (with the least kinetic energy) and will not be constantly moving. In the same way, the wheels automatically tend to the lowest energy consumption when turning, and automatically adjust the speed of the left and right wheels according to the turning radius.

When turning, due to the phenomenon of slipping and dragging on the outer wheel, the phenomenon of slipping on the inner wheel, the two driving wheels will produce the additional force in opposite directions at this time, due to the "principle of minimum energy consumption", the speed of the wheels on both sides will inevitably be different, thereby destroying the balance relationship of the three, and reflected on the half-shaft gear through the half-shaft gear, forcing the planetary gear to produce rotation, so that the speed of the outer half-shaft is accelerated, and the speed of the inner half-shaft is slowed down, so as to realize the difference of the speed of the wheels on both sides.

What is the function of a differential? Star Awareness Project

The differential of the car can make the left, right, or front and rear drive wheels, realize the mechanism of rotating at different speeds.

It is mainly composed of left and right half-shaft gears, two planetary gears and gear carriers.

When the car turns, the turning radius of the inner wheel and the outer wheel is different, and the turning radius of the outer wheel is greater than the turning radius of the inner wheel, which requires that the rotation speed of the outer wheel is higher than that of the inner wheel when turning.

The function of the differential is to meet the requirements of different wheel speeds on both sides when the car is turning. This role is the most basic role of the differential, as for the development of the first differential, anti-skid differential, LSD differential, Torsen differential, etc., they are designed to improve the driving performance and handling performance of the car.

High friction self-locking:

The high-friction self-locking type has a friction plate type and a slider cam type. The friction plate type locks the differential through the friction torque generated when the friction plate is relatively sliding between the friction plates, and this differential lock has a simple structure and works smoothly, and is most common in cars and light vehicles;

The slider cam type uses the larger friction torque between the slider and the cam to lock the differential, which can improve the passing performance of the car to a large extent, but the structure is complex, the processing requirements are high, the friction parts wear large, and the cost is higher.

Both of the above two high-friction self-locking differential locks can distribute the output torque of the left and right wheels within a certain range, and the access and disengagement are carried out automatically, so they are increasingly widely used.

The differential is because when the car is turning, the path taken by the outside wheels is larger than that taken by the inside wheels, so if the car wants to turn smoothly and precisely, it needs a device that can convert and allow the inner and outer wheels to rotate at different speeds, so as to compensate for the difference in distance at different speeds.

The earliest differentials were invented in Chinese guide cars to power dolls, but they did not appear in large quantities until the general use of automobiles in the industrial era, and the power was also exported from the engine to the wheels in reverse.

What is the function of a differential? Star Awareness Project

The car differential has three major functions, the first is to transmit the power output of the engine to the wheels: secondly, the increased torque of the final reducer is divided into two and distributed to the left and right half shafts; Finally, it acts as the main reduction gear of the car, reducing the speed of the drive train before the power is transmitted to the wheels, transmitting power to the wheels, and allowing the wheels on both sides to rotate at different wheel speeds.

The differential is composed of small bevel gears, large basin gears, and planetary gears, and the planetary gears are mounted on the large basin gears. The small bevel gear drives the large basin gear to rotate, and the planetary gear also rotates with the large basin gear, and the wheels on both sides run at the same speed, which is called revolution.

When one side of the wheel is subjected to resistance, the rotational speed decreases, and the reduced rotational speed is replaced by the rotation of the other planetary gear set, which means that the rotational speed increased on this side is the rotational speed decreased on that side.

The function of the differential is to ensure that the driving wheels rotate at different speeds while transmitting power.

The differential can change the direction of transmission of power and increase torque.

The differential has three functions: to transmit the power from the engine to the wheels; Acts as a reduction gear; The two wheels are allowed to rotate at different speeds, so as to meet the unequal distance of the wheels on both sides in the form of pure rolling as much as possible, reduce the friction between the tires and the ground, and ensure the smooth steering of the tractor.

The car differential is the main component of the drive axle. Its function is to transmit power to both side half shafts at the same time, allow the two side half shafts to rotate at different speeds, meet the two sides of the wheel as far as possible in the form of pure rolling unequal distance driving, reduce the friction between the tire and the ground. The trajectory of the wheels of the car when turning is an arc, if the car turns to the left, the center of the arc is on the left side, in the same time, the right wheel walks in an arc longer than the left wheel, in order to balance this difference, the left wheel should be slower and the right wheel faster, with different speeds to make up for the difference in distance.

When the car turns, the distance passed by the left and right wheels is inconsistent, for example, the car turns to the left, the center point of the turning arc is on the left side of Changpai, in the same time, the arc distance of the right (outside) wheel is usually longer than that of the left (inside) wheel, and if the two wheels are fixed on the same shaft, and the speed of the two wheels is the same, then the wheel will definitely slide while rolling, and this situation will also produce resistance and cause the vehicle to become extremely unsmooth when turning. There are even situations where it is impossible to turn. To improve this situation and enable the car to turn smoothly, it is necessary to make the left wheel rotate a little slower and the right wheel rotate a little faster, and make up for the difference in distance through different speeds. In order to solve this problem, a hundred years ago, the founder of the French Renault car Louis ( check price |Renault invented the differential.

The inside of the differential is mainly composed of spiral ring gears (main gears), planetary gears and left and right shaft gears, the vehicle equipped with the differential will pass through the gearbox when passing through the curve, and the main drive shaft transmits the power to the differential to make the large spiral ring gear rotate, although the speed of the wheels on both sides is inconsistent when cornering, but after passing the planetary gear, the different speed difference between the left and right wheels can be adjusted by itself, so that the vehicle can complete the corner comfortably.

Although the differential allows the wheels to complete the corner smoothly, if one of the wheel drive wheels slips or idles, the vehicle loses traction. This is due to the fact that when one side of the wheel suddenly loses grip, the resistance encountered by this side of the wheel is resistant, but the resistance of the other side of the wheel is very large, when the spiral ring gear rotates in the same wax type, the planetary gear used to adjust the speed of the wheel will also keep rotating itself, and the power will be continuously transmitted to the side of the wheel that loses grip, resulting in the vehicle can not move forward and can only spin in place. The solution to the above situation is to limit the operation of the differential to a certain extent, so that special differentials such as limited-slip differentials and differential locking are created.

To sum up, the car differential has three major functions, the first is to transmit the power output of the engine to the wheels: secondly, the increased torque of the final reducer is divided into two and distributed to the left and right half shafts; Finally, it acts as the main reduction gear of the car, reducing the speed of the drive train before the power is transmitted to the wheels, transmitting power to the wheels, and allowing the wheels on both sides to rotate at different wheel speeds. (Photo by photo:.)

Xie Hongmei) @2019

Function 1: Change the direction of power transmission. For example, in front-mounted rear-wheel drive models, the force transmitted by the gearbox passes through the bevel gears (i.e., driving gears &driven gears) arranged vertically and horizontally in the differential, and the transverse rotation force becomes a longitudinal rotation force, which smoothly drives the wheels forward.

Effect 2: Decelerate and increase torque again. In the last column, I talked about an example of an uphill model, and the transmission ratio of the 1st gear is 4:

1。The engine speed was reduced by a factor of 4 and the torque was amplified by a factor of 4, which was the "first torque increase". Suppose the ratio of the driving gear to the driven gear in the differential is also 4:

1. Then the force transmitted by the gearbox is amplified by 4 times again, and the speed is reduced by 4 times, which is the "second increase in torque". Assuming that the torque output of the engine is 1 n·m, then after two decelerations and torque, the final torque transmitted to the wheels is 1*4*4=16n·m.

Why not take advantage of the gearbox to increase the torque by 16 times at the beginning? This is because if the gear ratio is set to 16:1 (i.e., the input shaft rotates 16 times and the output shaft rotates 1 turn), the diameter of the gearbox output gear rises and is too large, which is not convenient for transmission design and installation.

Effect 3: Realize the speed difference between the left and right wheels. Suppose the vehicle makes a right turn, and the distance traveled by the right (inside) wheel is less than that of the left (outside) wheel.

And if the speed of the gearbox output to the left and right wheels is the same, and the distance traveled by the left and right wheels should also be the same, then the vehicle cannot steer at all. The function of the differential is to reduce the speed of the right (inside) wheel and increase the speed of the left (outside) wheel, so as to ensure the normal steering of the vehicle.

The differential is a mechanism that can make the left and right drive wheels move at different turning speeds, and its function is to meet the requirements of different speeds of the wheels on the two slip sides when the car turns, so that the car can pass the corner smoothly.

The differential has three functions: to transmit the power from the engine to the wheels; Acts as a reduction gear; The two wheels are allowed to rotate at different speeds to meet the needs of the wheels on both sides, and the sails can be driven at an unequal distance in the form of pure rolling, so as to reduce the friction between the tires and the ground and ensure the smooth steering of the tractor.