RV transmission is a new type of transmission developed based on the cycloidal pinwheel transmission. It has a series of advantages such as small size, light weight, wide range of transmission ratio, and high transmission efficiency. Compared with pure cycloidal pinwheel planetary transmission, it has smaller volume and larger overload capacity, and the output shaft has high rigidity. In the transmission mechanism of Japanese industrial robots, it has gradually replaced pure cycloidal pinwheel planetary transmission and harmonic drive to a large extent.
RV reducer consists of two parts: the involute cylindrical gear planetary reducer and the cycloidal pinwheel planetary reducer. If the involute central gear rotates clockwise, the involute planetary gear rotates counterclockwise while revolving, and it drives the cycloidal wheel to perform eccentric motion through the crankshaft. At this time, the cycloidal wheel not only revolves around its axis, but also rotates in the opposite direction, i.e., clockwise. At the same time, the crankshaft drives the output mechanism of the steel frame structure to rotate clockwise.
The existing RV reducer's first-stage reduction device adopts the involute cylindrical gear planetary mechanism. This mechanism consists of a gear shaft (the gear on the gear shaft can be called the central gear) and the planetary gear. The gear shaft adopts a cylindrical spur gear structure, which puts forward higher requirements for the assembly accuracy of the involute gear planetary mechanism.
To improve the assembly accuracy, it is necessary to improve the gear manufacturing and processing accuracy. At present, the gear processing accuracy in China is generally level 7, while the manufacturing accuracy requirements for the central gear and planetary gear of high-precision RV gears at robot joints are 5-6 levels.
Additionally, in order to compensate for manufacturing errors, facilitate assembly and ensure lubrication, there must be a certain amount of backlash between the gears. The existence of backlash is an inherent factor due to geometric deviations.
Furthermore, by examining the performance of imported RV gears under standard conditions, even if the manufacturing accuracy of the central gear and planetary gear reaches levels 5-6, the gear backlash is still not ideal, leaving room for improvement and optimization.
How to minimize gear backlash as much as possible, reduce the requirements for manufacturing accuracy and assembly precision, and thus reduce backlash deviation and improve motion accuracy, is one of the challenges in manufacturing RV reducers.
The transmission of the new type of robot RV reducer is a new type of transmission based on cycloidal pinwheel, which has the advantages of small size, light weight, high transmission ratio, high transmission efficiency, and lower transmission shaft rigidity compared to pure cycloidal pinwheel planetary transmission. It has gradually replaced the single cycloidal pinwheel planetary transmission. It is a pure cycloidal pinwheel planetary harmonic transmission.
The new robot RV reducer consists of cylindrical gears, involute planetary gear reducers, cycloidal pinwheel planetary gear reducers, involute 3-4 planetary gear reducers, and a crankshaft. If the center of the input involute gear rotates clockwise, then the center of the involute planetary gear also rotates clockwise in a C-V curve. The output mechanism of the cycloidal wheel steel frame is also driven by the crankshaft.
In the first stage of the RV reducer, the involute cylindrical gear mechanism consists of gear shafts and gear axles, which can be called the central gear. It adopts structures such as cylindrical gear shafts and spur gear axles.
In order to improve the assembly accuracy and processing precision of the involute planetary gear, the current domestic gear processing accuracy is usually level 7. However, if high-precision robot RV reducers are imported from abroad, it will undoubtedly greatly increase the manufacturing cost.
In addition, in order to compensate for manufacturing errors, facilitate disassembly, ensure lubrication, it is also necessary to study the working performance of imported RV gears in order to eliminate gear backlash. Even if the processing center's planetary gear accuracy meets the standard under standard conditions.
How to reduce gear backlash, lower the requirements for manufacturing accuracy and assembly precision, and thus reduce backlash, is a perpetual challenge that all RV reducer manufacturing companies need to overcome.