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In view of its limited installation space and high bearing requirements, reducer bearings for industrial robots are often designed as thin-walled and non-standard bearings. Due to the high precision requirements of reducer movement, the processing and manufacturing requirements of bearings are very strict. According to their different applications, they are mainly divided into the following categories: RV Reducer bearing, harmonic reducer bearing, bearing for cycloid needle wheel reducer, etc.
RV Reducer is developed on the basis of cycloidal pinwheel drive, using a two-stage reduction and central disc support structure. It has the advantages of a large transmission ratio, high transmission efficiency, high motion accuracy, small return difference, low vibration, high rigidity and high reliability. It is the “Royal” reducer of the robot. The key of the reducer lies in the precise positioning of the bearing, which requires the excellent performance of the bearing, such as large output torque, high precision, large load, small volume, lightweight, high rigidity, low noise, long service life, stable operation, safety and reliability, long-term continuous work in a harsh working environment and high impact resistance. It is mainly used in precision transmission industries requiring small space and large speed ratio, such as robots, welding positioner (turnover table), CNC machine tools, precision radar drive control, etc.
This type of bearing is mainly used as the main bearing of the reducer, with a large contact angle, usually 40 ° ~ 50 °, with high precision and high rigidity, which has an important impact on the torque rigidity of the reducer; The inner and outer rings of the bearing are usually unequal in height. On the one hand, due to the compact structure of the reducer, the interference of the bearing in the installation process is avoided. On the other hand, it is also convenient for the lubrication and heat dissipation of the bearing; The bearing cage usually adopts the crown cage of PA66 injection molding.
1.2 thin wall deep groove ball bearing
This kind of bearing is mainly used in the output part of the reducer, which requires high precision and stable output.
1.3 thin wall tapered roller bearing
This kind of bearing is divided into crank support and main body support. The thin-walled tapered roller bearing for crank support is usually small and placed on both sides of the crank to support the crank; Thin wall tapered roller bearing for main support has a similar function to thin wall angular contact ball bearing and is used as the main bearing of reducer.
1.4 cylindrical roller (needle roller) and cage assembly
This kind of bearing has no inner and outer rings. When in use, it is placed in the middle of the crank. The matching shaft and hole are used as the inner and outer rings and raceways of the bearing to support the crank cycloid wheel. The structure is very compact.
A harmonic reducer used to be the main device for robot joint transmission. It realizes motion transmission through the elastic deformation of a flexible wheel, and the elastic deformation is large. Due to the large elastic return difference caused by elastic deformation, the accuracy of robot motion is affected. It is mainly used in robot forearm, wrist or hand. When the harmonic reducer transmits load, the deformed flexible wheel and rigid wheel are not meshed with conjugate tooth profile, resulting in low guaranteed motion accuracy and life. Therefore, in recent years, RV Reducer has gradually replaced many high-precision robot transmissions. The flexible bearing required by the harmonic reducer is the key component to make it move. This kind of bearing will produce periodic alternating stress in the process of use. In addition, the bearing wall thickness is thin, which puts forward high requirements for bearing materials and processing and manufacturing.
Cycloid pin gear reducer is a kind of transmission device which applies the principle of planetary transmission and adopts cycloid pin tooth meshing. A 180 ° offset double eccentric sleeve is installed on the input shaft, and two roller bearings called the rotating arm are installed on the eccentric sleeve to form an H mechanism. The roller bearing has no bearing outer ring, and the center holes of the two cycloidal wheels are used as the outer ring and raceway of the rotating arm bearing on the eccentric sleeve.
In addition to the above three types of reducers, there are other types of reducers, such as planetary reducers. The reducer for industrial robots requires a compact structure, high output power, short transmission chain, lightweight and easy control. RV Reducer and harmonic reducer are mainly used in industrial robot reducers.