With the development of the Chinese industrial robot industry, the demand for RV gearboxes in the Chinese robot industry has shown a continuous growth trend. Although it has to some extent driven the synchronous development of the Chinese gearbox industry, the majority still relies on imports.
According to the analysis of the global and Chinese RV gearbox industry development status in 2022, Japanese companies occupy a large market share. The reason behind this is simply that they cannot match the manufacturing precision of foreign counterparts.
The existing RV gearboxes use a cycloidal gear planetary mechanism for the first-stage reduction device. This mechanism consists of a gear shaft (the gear on the gear shaft can be referred to as the central wheel) and planet wheels. The gear shaft adopts a cylindrical straight-tooth gear structure, which places high demands on the assembly precision of the cycloidal gear planetary mechanism. To improve the assembly precision, the gear manufacturing and processing precision must be increased.
What are difficulties in the current Chinese gearbox industry?
Currently, the gear processing precision in China is generally at level 7, while the manufacturing precision requirements for the central wheel and planet wheels of high-precision RV gears used in robot joints are at levels 5 to 6. If advanced precision manufacturing equipment from abroad is used, it undoubtedly significantly increases the manufacturing cost, especially considering that some precision manufacturing equipment is still in a "technological blockade" stage. Achieving domestic substitution has become one of the difficulties in the current Chinese gearbox industry.
It is well understood that in order to achieve Chinese substitution for Japanese technology, breakthroughs must be made in terms of durability and cost. It is precisely under this concept that a new transmission technology has been developed.
The newly developed transmission technology, combined with disruptive innovation in structure, allows the newly developed high-precision micro cycloidal gearbox to not only reduce the difficulty of manufacturing and assembly but also achieve a transmission design with a large speed ratio. As a result, it has gradually replaced single cycloidal needle wheel planetary transmissions and pure cycloidal needle wheel harmonic transmissions.
The core component of the high-precision micro cycloidal gearbox is the cycloidal gear, which adopts an arc-shaped design with R-angle teeth. The teeth are larger and smoother, achieving higher transmission precision through multiple engagements with high-precision rolling pins, while maintaining a small size and large speed ratio.
A new transmission technology has been developed
In high-speed operation, the design of R-angle teeth is more wear-resistant and impact-resistant, making it suitable for frequent forward and reverse rotations.
This gearbox itself adopts a unique flange design. In addition to meeting customers' requirements for flange output, adding a shaft on the flange surface can transform it into a shaft output similar to a planetary gearbox, meeting customers' requirements for shaft output with higher precision (≤1 arc minute).
Comparison with harmonic drives: Harmonic drives can achieve a very compact size due to their fine structure, but their load-bearing capacity is generally lower, requiring additional bearings. The rigidity is not as good as RV gearboxes, and there is sliding friction between the wave generator, flex spline, and circular spline, resulting in significant precision loss during long-term operation, and the rigidity will decrease over time.
Comparison with planetary gearboxes: Planetary gearboxes have excellent load-bearing capacity but are relatively larger in size. The minimum transmission loss for planetary gearboxes is only about 3 arc minutes. Traditional gear transmission has sliding friction, resulting in higher noise levels.
The manufacturer who can make the cycloidal reducer the size of harmonic reducer must go to his own products and have: high rigidity, small size, high precision, large load and long life.