Abstract: Robotics technology is undergoing rapid and ever-changing innovations. The rapid development of industrial robots is inseparable from the continuous improvement of their core component technologies. One of the most critical core components of industrial robots is the RV reducer. Foreign RV reducers have undergone more than 30 years of development, and the technology is relatively mature. With the development of China's industrial robot industry, domestically produced RV reducers are also becoming increasingly sophisticated. Currently, domestically produced RV reducers still lag behind foreign brands to some extent. However, with continuous technological innovation and strong government policy support, domestically produced RV reducers will undoubtedly usher in a broader future.

Keywords: Domestic RV reducer; industrial robot; technological innovation

1. Definition and Importance of RV Reducers

    With the advancement of technology, all aspects of our lives and work are becoming increasingly intelligent. The development and application of robots embody the intelligentization of modern life. Among the most critical technical components of robots is the RV reducer. The cost of an industrial robot is comprised of: robot body 22%, servo system 25%, reducer 38%, control system 10%, and other 5%. GGII data shows that in 2017, the demand for RV reducers in China's industrial robot industry reached 319,600 units, a year-on-year increase of 63.9%; the market size reached 2.24 billion yuan, a year-on-year increase of 45.4%.

 

1.1 Definition of RV reducer

 

    The RV reducer consists of a planetary gear reducer (front stage) and a cycloidal pinwheel reducer (rear stage). The RV reducer is a compact transmission mechanism with a large transmission ratio and self-locking function under certain conditions. Developed from traditional pinwheel planetary transmissions, the RV drive not only overcomes the shortcomings of general pinwheel transmissions but also possesses a series of advantages such as high precision (backlash less than 1 arcminute), high rigidity, high durability, high output density (strong torque & compact design), a wide reduction ratio range, and low vibration.

 

1.2 The Importance of RV Reducers to Industrial Robots

 

    The J1-J4 joints of industrial robots generally use RV reducers. Light-duty industrial robots may use low-load harmonic reducers for the J5-J6 joints. An average industrial robot uses 4.5 RV reducers, highlighting their importance.

 

    The power source for industrial robots is an AC servo motor. To ensure the robot can reliably complete tasks and guarantee process quality, high repeatability and positioning accuracy are required. This necessitates the use of a high-precision RV reducer. Another function of the RV reducer is to reduce speed and increase torque. When the load is large, continuously increasing the motor power is not advisable. In this case, the best shortcut is to increase the output torque through an RV reducer.

   Furthermore, motors are prone to overheating and low-frequency vibrations when operating at low frequencies, which is detrimental to ensuring the accuracy and reliability of the robot. RV reducers enable the motor to operate at a suitable speed and precisely reduce the rotational speed to the speed required by various parts of the industrial robot, improving the rigidity of the mechanical body while outputting greater torque.

 

2. Development and Current Status of RV Gear Reducers Abroad

 

    The earliest concept of a planetary pinwheel drive was proposed in 1926 by Lorenz Brown, a German engineer. Around 1980, Teijin Seiki of Japan developed the RV drive theory and began applying RV drives to the robotics industry, achieving great market success. They now hold over 60% of the global RV reducer market. Other well-known foreign companies producing RV reducers and similar products include Sumitomo of Japan and Spina of the Czech Republic.

 

3. Development and Current Status of RV Gear Reducers in China

 

    Although RV reducers play a crucial role in industrial robots, most domestically produced industrial robots in China still rely on imported RV reducers. In response, during the 12th Five-Year Plan period, the National 863 Program listed RV reducers as a key technological bottleneck to be overcome. With strong national policy support and the continuous development of China's RV technology, domestically produced RV reducers are becoming increasingly sophisticated. However, despite these achievements, compared with similar foreign products, there are still many shortcomings in overall performance, precision, lifespan, load-bearing capacity, stability, and consistency, which require further improvement.

    According to statistics, there are 353 robot companies in China, but only a dozen or so specialize in RV reducers. Nantong Zhenkang began developing RV reducers in 2010 and has since completed the development of models such as RV-E and RV-C, which have been launched on the market. Wuhan Jinghua reportedly began independently developing a precision reducer that passed testing in 2014. Qinchuan Development also announced in 2014 an investment of 194 million yuan in a technical upgrade project to produce 90,000 sets of RV reducers. Among listed companies, Julun, Siasun, Zhongda Lide, and Shuanghuan have all announced their involvement in the research and application of RV reducers. The domestic RV reducer market is now fiercely competitive.

 

4. Future Prospects of RV Gear Reducers in China

 

    In recent years, although the R&D technology of domestically produced RV reducers has improved significantly, well-known domestic and international robot companies, such as the four major robot manufacturers KUKA, ABB, FANUC, and Yaskawa, have not yet begun to adopt domestically produced RV reducers in large quantities. Domestically renowned robot companies such as Siasun, ESTUN, EFORT, and Guangzhou CNC are mostly only in the testing or small-batch trial stage of domestically produced RV reducers. The reasons for this include factors such as product quality and technical after-sales service. Therefore, if domestically produced RV reducers want to further penetrate the robot market, they still need to improve the following aspects.

 

4.1 Improve quality

 

    Currently, domestically produced RV reducers still lag behind foreign products in terms of service life, transmission accuracy, noise, and stability. On the one hand, the technology for domestically produced products is still under development; on the other hand, their application in the market is limited, lacking an environment conducive to quickly identifying problems. Therefore, domestically produced RV reducers should rapidly expand their market reach and be applied more extensively in various fields. Based on market feedback, products should be improved and technologies refined in a timely manner, extracting the essence from practical experience.

 

4.2 Reduce costs

 

    Increased production leads to lower procurement costs; conversely, high procurement costs hinder increased production. Domestic RV gearbox manufacturers currently face a similar predicament. It is recommended that domestic manufacturers utilize standard components as much as possible, focusing on developing specific RV models to effectively increase production and expand their bargaining power regarding procurement costs.

 

4.3 Sub-sectors

 

    Currently, most domestically produced RV gear reducers reference the technical specifications and application areas of Japanese RV gear reducers when promoting their products. While this facilitates product comparison, it's unlikely that domestic gear reducers will be able to compete with foreign products in all tenders in the short term. Manufacturing is a gradual process requiring accumulated experience and technological refinement. Therefore, at this stage, it's advisable to focus on specific niche industries, emphasizing certain technical specifications while relaxing others to facilitate rapid expansion.

 

4.4 Improve after-sales service

 

    Due to geographical and cultural advantages, the primary battleground for domestically produced RVs is naturally the domestic robotics industry. Therefore, delivery times and after-sales response times are significant advantages. Currently, some foreign RV manufacturers do not yet have branches or offices in China. Therefore, domestic RV manufacturers should leverage this advantage to gain customer favor as soon as possible through strong technical support and after-sales service.

 

4.5 Technological Innovation

 

    Most domestically produced RV reducers are classified as RV-E (solid), RV-C (hollow), and RV-N (solid), etc., which are based on existing foreign product series. Currently, the existing models can meet the needs of the robot market.

 

    However, from a long-term perspective, domestically produced RV gearboxes do not need to always follow foreign brands; they can certainly innovate independently. In particular, the booming development of the Chinese robot market and the proliferation of applications provide a favorable external environment for technological innovation in domestically produced RV gearboxes. Domestic RV gearbox manufacturers should seize this opportunity, be bold in innovation, and continuously explore new avenues to strive to lead the industry's development as soon as possible.

 

4.6 Going to the International Market

 

    With the continuous maturation of domestic RV reducer technology and the continuous increase in production, domestic RV reducers can not only develop in the domestic robot market, but also look to the global robot market, compete with foreign competitors, and enter the international market.

 

5 Conclusion

 

    With the help of the development of robotics and the support of national policies, the domestic RV reducer industry will surely usher in a broader space for development through continuous exploration and development.

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