Why is backlash required between teeth in gear transmission?
Gear transmission, gear manufacturers seem to have been committed to improving gear accuracy, using different methods to enhance the precision of each gear and the accuracy of gear meshing:

Definition of backlash in planetary gearbox

The backlash of a planetary gearbox, also known as the return clearance, refers to the angular displacement of the gearbox's output or input when the gearbox rotates clockwise and counterclockwise at the output or input end to generate a certain torque. It is generally expressed in degrees and is measured in arcmin, where 1 degree equals 60 arcmin.

Backlash is an important parameter of precision planetary gearbox, and the lower the value, the higher the accuracy. Generally, high-precision type is defined within 3 arc minutes, and low precision type is defined above 15 arc minutes. The backlash has a significant impact on the performance and lifespan of the gearbox. If the backlash is too large, it will cause obvious relaxation during reverse rotation, affecting the positioning accuracy and motion stability of the gearbox. Conversely, if the backlash is too small, it will cause meshing interference or jamming, increasing the friction and wear of the gearbox, thereby reducing its lifespan.

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However, the gear clearance of meshing transmission is too small or there is no clearance, which brings disaster to the movement of the gears.

In fact, in order to achieve smooth and fluent rotational transmission in gear transmission, there needs to be side clearance. Side clearance refers to the clearance between the tooth surfaces of a pair of gears when they mesh. According to the measurement direction, it is classified as follows:

1. Circumferential side clearance

In a gear pair, the length of the pitch arc that one gear can rotate while the other gear is fixed is called the circumferential backlash.

2. Lateral clearance in normal direction:

The shortest distance between the non meshing tooth surfaces of two gears when they come into contact with each other is called the normal backlash.

3. Rotation angle side clearance

The maximum angle that one of the gears can rotate when the gear pair is fixed at the standard center distance.

4. Radial side clearance

The difference between the center distance and the predetermined center distance when the meshing side tooth surface and the non meshing side tooth surface are in contact at the same time is called lateral clearance.

5. Axial side clearance

The difference between the assembly distance and the predetermined assembly distance when the meshing and non meshing tooth surfaces of a bevel gear are in contact simultaneously is called axial backlash.