This article will analyze the differences between spur gear planetary gearboxes and helical gear planetary gearboxes from various aspects such as construction, precision, transmission torque and efficiency, axial force, and load capacity.

Construction

Spur Gear Planetary Gearboxes:

The internal sun gear, planetary gears, and ring gear all feature spur gear meshing.

Helical Gear Planetary Gearboxes:

The internal sun gear, planetary gears, and ring gear all feature helical gear meshing.

Meshing Characteristics and Smoothness

Spur Gears:

Meshing involves the "entire tooth width" making instant contact and separation. This leads to sudden loading and unloading of force, causing impact and vibration, which is a primary source of noise.

Helical Gears:

Meshing is a gradual process from the tip to the root of the tooth. More pairs of teeth are in contact simultaneously (higher contact ratio). The transmission process is like a "relay race," with force transferred smoothly between teeth, resulting in extremely smooth operation and low noise.

Precision

Spur Gear Planetary Reducer:

First-stage precision is within 10 arcminutes, with fine precision reaching 6 arcminutes.

Helical Gear Planetary Reducer:

First-stage precision is around 5 arcminutes, with fine precision under 1 arcminute.

Axial Force Issue

Spur Gears:

Theoretically, no axial force is generated. Bearings only need to handle radial forces, simplifying the design.

Helical Gears:

Due to the helix angle, significant axial force components are generated during gear meshing. This force must be counterbalanced by bearings capable of withstanding axial thrust (such as angular contact ball bearings), which increases the complexity and cost of the bearing system.

Load Capacity and Size

Under the same module and center distance, helical gear planetary gearboxes have higher load capacity and torque density because more teeth are in contact simultaneously and the contact line is longer. This means that to achieve the same output torque, a helical gear reducer can be designed more compactly (smaller volume, lighter weight), or it can handle a greater load within the same volume.

Transmission Torque and High Efficiency

Spur Gear Planetary Gearboxes:

With the same motor shaft, spur gear meshing results in relatively lower transmission torque compared to helical gear gearboxes and lower transmission efficiency.

Helical Gear Planetary Gearboxes:

With the same motor shaft, helical gear meshing provides greater transmission torque than spur gear gearboxes, along with more stable transmission, higher strength, and higher efficiency.

Planetary gearboxes offer higher transmission efficiency. In high-power planetary reducers, helical gears provide greater torque and more stable transmission. Even small-power reducers may use helical gears to reduce transmission backlash and error.