How the planetary gear structure is used in automobiles

Update:13-05-2022
Summary:

The invention of the planetary gear automatic transmiss […]

The invention of the planetary gear automatic transmission makes the operation of the car more convenient and labor-saving, and the comfort has also been greatly improved. Locking the central differential and variable distribution of power to the front and rear axles increase the car's passability, thanks largely to the mysterious planetary gear mechanism. For most friends who love cars, this little thing is both magical and complicated, and it is difficult to understand it thoroughly.

The planetary gear mechanism is the main mechanical transmission part in the transmission. In the Torsen differential is the locking and front-to-rear axle torque distribution mechanism. If you want to master the working principle, you must first master the power transmission method of the single-row planetary gear mechanism.

The sun gear is located at the center of the entire mechanism like the sun, the planet gears mesh with the sun gear, and the internal gear design of the ring gear allows the ring gear to mesh with the planet gears on the planet carrier. There are usually 3-6 planetary gears (4 planetary gears in the above picture) symmetrically and evenly mounted on the needle roller bearing through the needle roller bearing. When the planetary gear mechanism is working, in addition to the rotation around its own axis, the planetary gear can also revolve around the sun gear, and the planet carrier also rotates around the sun gear. Since the sun gear and the planetary gear are externally meshed, the rotation directions of the two are opposite. of. The planetary gear and the ring gear are in internal meshing. The direction of rotation for both is the same. The sun gear, ring gear and planet carrier and planetary gear are usually referred to as the four basic elements.

According to the basic principle of gear transmission: the large gear with the small gear increases the speed, and the pinion with the large gear reduces the speed. The internal meshing steering is the same, and the external meshing steering is opposite. Each time a gear is added, the direction changes once, according to the basic principle.
It is assumed that the active element rotates clockwise before the analysis.

(1) The planet carrier is active, the ring gear is driven, and the sun gear is fixed, forming a state of increasing speed in the same direction. The planet carrier with more teeth drives the ring gear with fewer teeth to rotate, and the speed increases. To the speed-up state, that is to say, the planet carrier rotates clockwise, the ring gear must also rotate clockwise, and the speed increases.

(2) The planet carrier is active, the sun gear is driven, and the ring gear is fixed, forming a state of increasing speed in the same direction. The planet carrier with more teeth drives the sun gear with less teeth to rotate, and the speed increases more, and because it is internal meshing, so form a state of increasing speed in the same direction.

(3) The sun gear is active, the planet carrier is driven, and the ring gear is fixed to form a state of deceleration in the same direction. The sun gear with less teeth drives the planet carrier with more teeth to rotate and decelerates more. Due to the meshing of the other parts, the same-direction deceleration state is formed.

(4) The sun gear is active, the ring gear is driven, and the planet carrier is fixed, forming a reverse deceleration state. The sun gear with a smaller number of teeth drives the ring gear with a larger number of teeth to rotate, and the speed is reduced, and because the planet carrier is fixed, the planet gear is idle wheel, so a reverse deceleration state is formed.

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