What are the functions of planetary gears

Update:24-10-2020
Summary:

In addition to planetary gears that can rotate around t […]

In addition to planetary gears that can rotate around their own axis of rotation (B-B) like fixed-axis gears, their axis of rotation also rotates with the blue carrier (called the planet carrier) around the axis of other gears (A-A). The rotation around its own axis is called "rotation", and the rotation around the axis of other gears is called "revolution", just like the planets in the solar system, hence the name.
Most of the gears known to us are gears with a fixed axis of rotation. For example, in mechanical clocks, although all the gears above are rotating, their rotation center (which coincides with the center of the circle) is often mounted on the case through a bearing. Therefore, their rotation axis is fixed relative to the case. Also called "fixed axis gear".
There must be movement. Correspondingly, there is a less well-known type of gears called "planetary gears". Their axis of rotation is not fixed, but is mounted on a rotatable bracket. Planetary gears can rotate around their own axis of rotation (BB) like fixed-axis gears, their axis of rotation also follows the blue carrier (called planet carrier) around the axis of other gears (AA) Rotate. The rotation around its own axis is called "rotation", and the rotation around the axis of other gears is called "revolution", just like the planets in the solar system, hence the name.Just like the solar system, the gears with fixed axes that become the center of planetary gear revolution are called "sun gears".

Function of planetary gear
(1) The planetary gear changes the transmission ratio to meet the traction requirements of different driving conditions, so that the engine works under favorable conditions as much as possible to meet the possible driving speed requirements. Change the speed of the car and the torque on the driving wheels of the car in a larger range. Due to the different driving conditions of cars, it is required that the driving speed and driving torque of the car can be changed in a wide range. For example, the vehicle speed on the highway should be able to reach 100km/h, while in the urban area, the vehicle speed is often around 50km/h. When an empty vehicle is driving on a straight road, the driving resistance is small, and when it is fully loaded uphill, the driving resistance is very high. The characteristic of the automobile engine is that the speed change range is relatively small, and the torque change range cannot meet the actual road conditions.
(2) Planetary gears realize reverse driving, which is used to meet the needs of reverse driving. To realize reverse driving of a car, the engine crankshaft generally can only rotate in one direction, and the car sometimes needs to be able to travel backwards. Therefore, the reverse gear set in the gearbox is often used to realize the car reverse.
(3) The planetary gear interrupts the power transmission, and the power transmission to the driving wheels is interrupted when the engine is started, idling, the car is shifted or needs to be stopped for power output.
(4) The planetary gear achieves neutral gear. When the clutch is engaged, the gearbox may not output power. For example, it can be ensured that the driver releases the clutch pedal and leaves the driver's seat when the engine is not stalled.

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