1. The challenge brought by the drive motor to the motor bearing
The motor bearings used in general industrial motors, the domestic bearing industry has undergone continuous development, with the improvement of the theoretical level of bearing design, the progress of bearing steel material technology, the improvement of ferrule processing equipment and process level, and the improvement of steel ball manufacturing level, It has already replaced imports to occupy the main domestic market, but the wide speed range, large starting torque, high power density, and high efficiency of automobile drive motors make it more important for the bearing's high speed, high and low temperature, durability, stability, and reliability. Higher requirements are put forward. At present, domestic new energy vehicle motor bearings still mainly rely on imports.
(1) Speed: The speed of the driving motor is as high as 20,000 r/min, and the shaft dm.n value reaches more than 800,000, which is much higher than the speed of ordinary industrial motors.
(2) Temperature: -40~150 ℃, the bearing runs stably without whistling; the long-term working temperature is 110~120 ℃; the starting temperature in cold regions is -30~-20 ℃, the starting torque is small, and the noise is low.
(3) Lubrication: Grease is required to have excellent low temperature performance, high temperature resistance, vibration resistance, energy saving and high efficiency, and long life.
(4) Vibration and noise: In order to ensure the comfort of the car, the vibration and noise level of the motor should be low to ensure the quietness of the car.
(5) Electric corrosion: Due to the unbalanced winding, there is a potential difference between the rotors, which forms a current; the current leakage caused by the high-frequency voltage of the inverter may cause electric corrosion in the bearing, resulting in failure of the bearing.
(6) Lifespan: Guaranteed to be 5-8 years or 100,000-160,000 kilometers the same as the vehicle warranty.
2. Countermeasures made by bearing companies
In the face of new challenges to bearing companies in new application fields, a lot of effort is required from independent research and development to industrialization:
(1) Improve steel purity and heat treatment quality;
(2) Adopt precision grinding technology to improve processing accuracy and reduce product batch dispersion;
(3) Carry out lubrication research and cooperate with lubrication companies to develop lubrication products suitable for high temperature and high speed;
(4) Select a suitable engineering plastic cage;
(5) Use simulation and test technology to speed up development, ensure bearing reliability, etc.
(6) Refer to the countermeasures proposed by internationally renowned bearing companies, such as:
① SKF has developed the eDrive ball bearing series. By optimizing the design of the raceway, designing a new structural polymer cage, using grease with a wide temperature range, and designing a hybrid ceramic bearing, it can adapt to the high-speed performance of the motor bearing and help extend the transmission. system life and extend battery life.
②NSK adopts resin materials with excellent heat resistance, and optimizes the shape design through cage strength analysis, thereby reducing centrifugal force, reducing friction between the cage and steel balls, and reducing heat generation;
③Using high-speed lubricating grease and selecting the most suitable thickener, which can reduce the calorific value in a wide temperature range;
④ Special treatment is adopted to precipitate high hardness nitrides on the surface of steel balls, which improves the sintering resistance and thus improves the high-speed running performance;
⑤Using non-contact rubber sealing ring to suppress the leakage of lubricating grease during work and ensure the reliability of continuous operation of the bearing;
⑥Set O-ring on the outer diameter surface to reduce the gap with the seat hole and improve creep resistance.
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