Qingdao Vanhon Machinery Technology Co.,Ltd.

Industry News
What is a planetary gear
May 17, 2022

1. Definition


In addition to being able to rotate around their own axis of rotation like fixed-axis gears, their axis of rotation also rotates with the planet carrier around the axes of other gears. The rotation around its own axis is called "rotation", and the rotation around other gear axes is called "revolution", just like the planets in the solar system, so it is called planetary gear.

What is a planetary gear(图1)

2. Classification


1). According to the number of planetary gear sets installed on the planet carrier, it is divided into single planetary row and double planetary row

Single planetary row: It is mainly composed of a sun gear (or called a central wheel), a planetary gear carrier with several planetary gears and a ring gear (ring gear). The sun gear and the planetary gear are externally meshed, and the rotation directions of the two are opposite; while the planetary gear and the ring gear are internally meshed, and the rotation directions of the two are the same.

Double planetary row: It is mainly composed of sun gear, ring gear, and planetary carrier with inner and outer planetary gears.

 

2). According to the space structure, it is also divided into plane planetary gears and space planetary gears

 

Planar planetary gear train: A planetary gear train composed of plane gears. It is characterized by the fact that all gear axes are parallel to each other. It is the most versatile planetary gear train.

 

Space planetary gear train: A planetary gear train containing at least one pair of space gear pairs. Its characteristics are. The axes of the gears are not completely parallel, and their relative steering relationship is represented by the speed vector symbol. This planetary gear train is used less.

 

3. Composition


Sun Gear: Usually the motor pinion. In a planetary gear train, the external gear as the sun gear.

Planet carrier: a member that supports the planetary gear shaft and rotates around the axis of the sun gear, generally with three to five planetary gears.

Planetary gear: It is generally installed on the planetary carrier and rotates on the planetary carrier support shaft. It is always in constant meshing state with the adjacent sun gear and ring gear. Helical gears are usually used to improve the stability of work. Occasionally rotates around the central axis of the sun gear.

Gear Ring: Usually in the housing. In a planetary gear train, the internal gear as the sun gear.


4. Transmission mode


Planetary gear transmission with fixed ring gear: The ring gear is fixed, and the sun gear and the planetary turret rotate in the same direction. The sun gear is a high-speed shaft, and the planetary turret is a low-speed shaft. The gear ratios used for this transmission are between 3:1 and 12:1.

 

Planetary gear transmission with fixed planetary turret: The planetary turret is fixed, and the sun gear and the inner gear rotate in opposite directions. The sun gear is a high-speed shaft, and the inner gear connecting shaft is a low-speed shaft. The gear ratio of this transmission is between 2:1 and 11:1.

 

Planetary gear transmission with fixed sun gear: The sun gear is fixed, and the planetary turret and the inner gear rotate in the same direction. The connecting shaft of the ring gear is a high-speed shaft, and the planetary turret is a low-speed shaft. The gear ratio range of this transmission is between 1.1:1 and 1.7:1.

 

5. Advantages


1) Because the internal layout loss of the gear is small, and the power can be split when the power is transmitted, so it has a very good efficiency level.

2) Because the gear has a large contact area and is always meshed, the wear is small, the noise is low, the motion accuracy and reliability are also high, and the service life is long.

3) The output shaft and input shaft of the entire planetary gear are on the same horizontal line.

4) The planetary gear has several planetary loads, so it has the advantages of high load and large transmission ratio, and there are many transmission ratios to choose from.

5) The overall small size, light weight, strong versatility.

 

6. Disadvantages


The complex structure and working state lead to prominent vibration and noise problems, especially gear fatigue pitting, tooth root cracks and even gear teeth or shaft fractures and other failure phenomena, thus affecting the operation accuracy, transmission efficiency and service life of the equipment. Seven, application It is widely used in reducers, speed increasers and speed changers in various mechanical transmission systems. It is also widely used in aircraft and vehicles (especially heavy vehicles), such as transmissions in automobiles.

 

7. Scope of application

 

It is widely used in reducers, speed increasers and speed change devices in various mechanical transmission systems. It is also widely used in aircraft and vehicles (especially heavy vehicles), such as transmissions in automobiles.


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