Development and Test Verification of High Temperature and High Speed ​​Deep Groove Ball Cage

In recent years, high-temperature and high-speed application conditions represented by new energy drive motor bearings have put forward higher requirements on the performance of bearings, and the manufacturing difficulty has also increased greatly. The application characteristics of bearings mainly include: 1) long life. The life requirement has been increased from 8 years and 100,000 kilometers to 10 years and 300,000 kilometers (800,000 kilometers for oil-lubricated bearings). 2) High speed. The most commonly used drive motor rotor support bearings for passenger cars are 6206-2RS, 6207-2RS, etc. The average speed is increased from the original 12000r/min to 16000r/min, and the latest requirement is 24000r/min; Tesla, BYD The application speed of the representative electric vehicle has reached 20,000 r/min, and the dm·n value has exceeded 1.1 million, which is more than three times the limit speed. 3) Rapid acceleration, the acceleration from 100 km to 20 to 30s is increased to 2 to 3s. 4) Large impact force, up to 30g. 5) High sealing performance requirements, such as anti-leakage grease, waterproof, anti-dust and other sealing performance requirements. In order to meet these requirements of the bearing, compared with the previous similar bearings, it needs to have higher precision, lower vibration and noise, lower friction torque, impact resistance, good sealing performance and so on. Therefore, in the research and development of high-speed bearings, it is necessary to optimize the structure, cage, grease, sealing ring, test technology, etc. in an all-round way. Among them, the cage design problem is one of the key factors. The following focuses on innovative high-temperature, high-speed The development and testing of high-speed cages for deep groove ball bearings are analyzed and explained. 1. The force of the cage The cage structure of the deep groove ball bearing mainly includes wave shape, S shape and crown shape. According to different application conditions and materials, there are various changes in the design structure details. With the development of high-speed deep groove ball bearings, from the standpoint of cage material alone, in recent years, deep groove ball bearings with a dm·n value of more than 650,000 have rarely used steel cages, and mostly used engineering plastic cages. Factors considered include: centrifugal force, strength, vibration and wear of the cage at high speeds. Engineering plastic cages have the advantages of light weight, low vibration (2-3dB lower vibration value than steel cages), and impact resistance. They have been widely used in motor deep groove ball bearings, especially high-speed motor deep groove ball bearings. Usually, the cage is regarded as a rigid body affected by a complex force system, and the forces mainly include: 1) the impact force and friction force on the interaction surface between the cage and the rolling body; 2) the contact between the cage and the guide rib of the ferrule Normal force and friction force of the surface (assuming the rib guides the cage); 3) centrifugal force of high-speed motion; 4) force caused by the unbalance of the center of mass of the cage; 5) gravity; 6) inertial force of the cage; 7) cage Rolling viscous resistance and stirring resistance with lubricants. Due to the unilateral opening of the crown-shaped plastic cage (Fig. 1), the center of mass deviates (unavoidably) from the cross-section of the center of rotation of the steel ball. During high-speed operation, due to changes in centrifugal force, contact angle, etc., complex motions such as differential motion, spin, and gyro will occur between the steel ball and the raceway. These motions will inevitably cause violent collisions to the cage and aggravate the wear of the cage. , heat and deformation. On the one hand, these movements will cause high-frequency wobbling and distortion at the bottom of the cage pocket. In addition, the bottom of the cage pocket is relatively weak (limited by the inner space of the bearing) and the material softens at high temperature, which may cause the bottom of the cage pocket to become soft. break. On the other hand, due to the high temperature caused by the asymmetry of the center of mass and differential sliding, spin sliding, gyroscopic sliding, etc., as well as being in the high temperature operating environment of the motor for a long time, the cage jaws may become soft and deformed; high-speed operation The cage tends to be ejected toward the bottom direction (the opposite direction of the claw mouth), the higher the speed, the higher the temperature rise, the greater the risk, which may cause the cage to lose its guidance and cause the bearing to fail. Figure 1 Crown-shaped engineering plastic cage 2. Innovation of cage structure Many companies at home and abroad have carried out many innovations and explorations in the structural design of high-speed deep groove ball bearing cages. 1) SKF Figure 2 shows the classic cage structure of SKF, which is the company's Explorer series products more than ten years ago, suitable for high-speed motor deep groove ball bearings. Figure 2 Structure of SKF's high-speed deep groove ball cage ), as shown in Figure 3; this year, NSK launched the third generation of the world's highest speed, high-speed ball bearings for electric vehicle drive motors (Figure 4).