Planetary Mechanisms
Planetary mechanisms differ from other gear mechanisms according to their gear design and working principles. In sequential and stepped gear mechanisms, all teeth rotate around their own axis and transmit motion and power, while in planetary mechanisms, the sun gear starts to move first and enables the planet gears to rotate. The single row simple planetary mechanisms in Figure 1.1 are supported in the cage with the help of a planetary pin that can rotate around its own axis. Mechanisms emerged in the grouping made according to the number of planet carrier arm that formed it. There is one carrier arm and there may be more than one planetary gear wheel on a planetary carrier arm. The sun and the ring gear wheel are one each. They are mechanisms created by keeping the number of mechanism elements to a minimum in accordance with the purpose of operation. It is made in helical, conical and straight tooth profiles. Basic forward rates can be negative or positive. It can be used as motion and power separator or adder. In Figure 1.2, the double-row combined planetary mechanisms are shown. The working principles of double row planetary mechanisms are the same. Its difference compared to single row simple planetary systems is that it offers different rotation ratio options and meets higher torque. Double-row combined systems may vary according to the number of stages, and the number of circle and sun gear will be at least two. More planetary rows can be added to provide the desired output speed and output torque.
Planetary mechanisms are machine elements that have been used for hundreds of years. Like other gear wheel mechanisms, planetary gear systems are a type of gearbox used in motion and power transmission. They are generally used in transmission systems of motor vehicles, transferring large torque and high transmission ratio. Although this kinematic performance of planetary gear mechanisms eliminates the problem of taking up much space in traditional gear mechanisms, the design stages take a more complex, difficult and long process compared to other gear mechanisms.
Definition of Planetary Mechanisms and General Statements
Planetary gear mechanisms got their name from their structure. There are many circular gears around a central gear (sun gear), such as the planets (planetaries) around the sun. In this system, if one of the three elements is kept fixed and the other one is moved, the movement is taken from the third element by decreasing or changing direction. If two elements are connected to each other or the same movement is given to both elements, the system is locked. In planetary mechanisms, the motion and power of the sun gear or ring gear is transferred to the carrier cage or arm via the planetary gear. In addition, the motion and power in the carrier cage are transferred to the sun gear or ring gear via the planetary gear. The planet, which means planet, is named because the gear wheel connected to the cage with the help of pins rotates both around itself and around the sun gear like a planet. Mechanisms with gear wheels with this feature are also called planetary gear mechanisms.
How Planetary Mechanisms Work
Planetary mechanisms are a set of limbs, the elements of which are connected to each other according to certain rules, which transmit the motion and power from the motor to the output limb depending on a certain function. The mechanism transforms the power and movement given to it into a certain value and transfers it to a desired location. Planetary gear mechanisms transmit motion and power between the shafts in which they are located. This is done with sun gear, ring gear, planet gear, carrier cage or arm. The exchange of power and motion in the mechanism takes place only between three elements. These are sun gear, ring gear and carrier cage or arm. The power from the motor is transferred to the sun gear of the first stage with the help of the connecting shaft and starts to rotate with the input speed. This rotational movement is transferred to the planet gears, which are fixed concentrically to the carrier cage with pins, and the planet gears rotate together with the cage around which the fixed circle is fixed. The cage of the first stage is connected to the sun gear of the second stage and transfers the revolution and moment from the first stage to the second stage. Likewise, the cage of the second stage is connected to the sun gear of the third stage and transfers the speed and torque from the second stage to the third stage. The cycle continues in this way according to the number of stages, and the desired output values are obtained by transferring the torque and speed from the last stage to the output shaft.
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