A planetary gearbox is a mechanical transmission device, also known as a planetary reduction box or gearbox. Its structural feature is that multiple planetary gears rotate around a sun gear. This mechanism design enables the planetary gearbox to reduce the transmission speed ratio and increase the torque of the motor proportionally. Planetary gearboxes have the characteristics of smooth transmission and large load-bearing capacity, and can achieve a large transmission ratio in a small space. They have a long service life, especially when their gears are steel parts, the life span can reach 1000 years.

The working principle of planetary gearboxes is based on planetary gear mechanisms, which are special gear configurations in which multiple planetary gears rotate around a sun gear. The design of this mechanism not only reduces the transmission speed, but also increases the torque of the motor proportionally. The core of the planetary gearbox lies in its unique gear arrangement, through which power can be transmitted from the sun gear to the planetary gears, and then from the planetary gears to the fixed outer ring gear, thereby achieving the effect of speed reduction and torque increase. Generally speaking, when power is input to the sun gear, the planetary gears rotate on the planetary carrier and mesh with the ring gear to transmit power. The design of this mechanism allows two or more components to be used as active or passive components, providing greater design flexibility and the transmission ratio can be adjusted according to specific application requirements.

‌1.Smooth transmission and large load-bearing capacity: The design of the planetary gearbox enables it to exhibit smooth characteristics when transmitting power, and at the same time has a large load-bearing capacity, which is suitable for application scenarios that need to withstand heavy loads.

‌2.Compact structure, small size and light weight: Compared with traditional gear transmission, planetary gear transmission utilizes power splitting technology to make the overall structure more compact, while greatly reducing the volume and weight, which has significant advantages in saving space and reducing weight.

‌3.High transmission efficiency: The symmetrical design of the planetary gear transmission enables the reaction forces acting on the center wheel and the swing arm bearing to balance each other, thereby improving the transmission efficiency. The general efficiency value can reach 0.97~0.99‌3.

‌4.Large transmission ratio‌: Planetary gear transmission can achieve a large transmission ratio, which is very useful for applications that require a wide range of speed changes. Its maximum transmission ratio can reach tens of thousands or hundreds of thousands. When used as a power transmission, the maximum transmission ratio can reach dozens or hundreds. 

‌5.Smooth movement, strong resistance to shock and vibration‌: Since several planetary gears with the same structure are evenly distributed around the center wheel, the force of the planetary gear and the swing arm is balanced, and the number of teeth involved in the meshing is increased, thereby achieving smooth movement and enhancing the ability to resist shock and vibration. ‌

1.Improve gear accuracy‌: The gear accuracy must be controlled within GB10995-887~8 levels. For gears with a linear speed higher than 20m/s, the pitch limit deviation, gear ring radial runout tolerance, and tooth tolerance must be stably achieved at level 7 accuracy. In the case of a gear with level 7 accuracy, the tooth part must be reversed to prevent tooth root bosses. 

‌2.Control the quality of raw materials‌: Using high-quality raw materials is a prerequisite for producing high-quality products. Strict chemical composition inspection, grain size determination, and purity assessment are carried out on raw materials to improve the adjustment of heat treatment deformation and the quality of tooth shape processing.

‌3.Prevent heat treatment deformation: After rough processing, the gear blank is made into a fine forging and normalized or quenched and tempered.

‌4.Ensure the accuracy of the gear blank: The dimensional accuracy of the gear hole is required to be within the range of ±0.003~±0.005mm, and the end face runout and radial runout of the gear blank are 6 levels, set within the range of 0.01~0.02mm.

‌5.Take gear cutting processing measures: Inspect the purchased gear tools and they must meet the AA level requirements. Inspect the gear tools after grinding, including the radiality of the front edge of the tool, the adjacent pitch difference of the chip groove, the maximum cumulative error of the chip groove pitch, and the parallelism between the front of the tooth and the inner hole axis.

‌6.Civilized production: Remove burrs and bumps to reduce noise caused by burrs and bumps.

‌7.Use special materials and heat treatment and surface treatment methods‌: Use powder metallurgy forming technology for high-frequency quenching, or use ink cast iron for soft nitriding, or use 40Cr material for soft nitriding or tooth copper plating.

Source:https://hillary.full-design.com/methods-to-reduce-the-noise-of-planetary-gearboxes-72559949