Rolling bearing is a rotating part of the drive motor, high speed, high temperature, frequent starting and stopping along with the impact of the main working conditions of electric vehicle drive motors, the development of a series of sealed deep groove ball bearings that can adapt to the conditions of the working conditions, to meet the hybrid bus, pure electric bus, pure electric passenger cars, pure electric mini-vehicles and a series of new energy vehicles drive motors to use. And they are widely used in the market.
Design and application characteristics
The design of bearings for driving motors takes into account good sealing performance, high temperature performance, low temperature performance, repeated start-stop performance, a certain amount of axial impact load, etc., optimizes the internal structure of the product, takes into full consideration of the bearing materials, heat treatment, machining accuracy, grease, installation and coordination of the product, so that the product performance has been greatly improved, and the limiting rotational speed can reach the limiting rotational speed of the conventional bearings 1.5 times. The limiting speed can reach 1.5 times of the limiting speed of conventional bearings.
Running speed affects both bearing and grease life. Therefore, when selecting bearings, bearing size, cage type, lubrication method, clearance and seal type must be considered. Currently used in new energy vehicle drive motors with speeds up to 18,000rpm and dmn values up to 800,000 or more.
Shaft and Housing Materials
Due to the expansion and contraction of materials, the coefficient of expansion is a key consideration when selecting materials for shafts and housings. Thermal expansion and contraction will directly affect the fit of the shaft and housing, and thus the internal clearance of the bearing. The material of the shaft in the field of drive motors is usually made of medium carbon steel and tempered, and the shell is usually made of cast aluminum or aluminum alloy, which reduces the overall weight of the motor and also greatly improves the speed of heat dissipation.
Seals and sealing materials are particularly important in environments with humidity, low temperature, high temperature and a lot of mud, water and dust. Need to consider the impact of seals on the product; to prevent lubricant leakage on the environment and product contamination, while the leakage of grease will cause bearing oil shortage, affecting the service life of bearings for driving motors.
Bearing temperature is one of the main causes of machine life. When there is a large temperature difference between the ambient temperature and the operating temperature of the bearing temperature, the bearings for driving motors will produce a temperature gradient. If the temperature gradient is large, check the internal clearance of the bearing to avoid unnecessary bearing damage.
High-speed bearings of new energy vehicle drive motors adopt high temperature resistant (≥180℃) engineering plastic cages, and medium and low-speed bearings adopt SPCC cages, which have good high-speed performance and low noise performance.
The precision level of the vehicle drive motor bearings all reach P6 level, and the internal parameters can reach P5, with extremely high rotational stability and low noise performance (noise level up to Z3 group).
The rated life of bearings for driving motors is defined as the number of revolutions (or the number of hours of operation at a constant rotational speed) that the bearing can reach before the rings and rolling elements first show signs of fatigue (spalling or fracture).
Laboratory test data and practical experience have shown that apparently identical bearings running under the same conditions will still have different life.
In general, bearing life depends on the conditions under which it is operated, but bearing installation and maintenance procedures also have a direct effect on bearing life, and despite many precautions, bearings can still fail prematurely. When this occurs, the bearing is carefully inspected to determine the root cause of the failure. Corrective action can only be taken once the root cause analysis has been completed.
Target life is a life value given by the manufacturer based on ideal values for load and speed. For example, a minimum life of 5,000 hours or one year at the maximum permissible load.
Under good operating conditions, bearings can achieve a longer life than would be expected by normal or conventional life calculations. Good operating conditions are achieved when the lubricant film effectively separates the rolling surfaces (raceways and rolling elements) or when surface damage due to contaminants is limited.
Development Trends of Bearings for Driving Motors:
- High-Performance Materials: Advancements in technology will lead to the use of high-performance materials to manufacture bearings that are more wear-resistant, corrosion-resistant, and capable of withstanding high temperatures. Advanced materials such as ceramics, special steel alloys, etc., will enhance the longevity and performance of these bearings.
- Smart and Digitalization: Bearings for driving motors will become more intelligent and digitally integrated in the future, equipped with sensors and monitoring systems. These smart bearings will be able to monitor real-time operating conditions, temperatures, vibrations, etc., providing alerts and fault diagnostics to prevent failures and improve maintenance efficiency.
- Self-Lubrication Technology: Self-lubricating bearing technology will further develop to reduce maintenance requirements. New self-lubricating bearings will maintain stable lubrication even under high-temperature or high-load conditions, reducing friction and wear.
- Energy Efficiency and Environmental Friendliness: In line with increasing global environmental awareness, future bearings will focus on energy efficiency and environmental sustainability. Manufacturers will optimize designs to reduce energy consumption and resource waste.