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New energy electric vehicles are green, zero-emission new energy vehicles advocated and developed by the state in recent years, in which the drive motor, battery and controller are the core components of new energy vehicles and the heart of new energy vehicles.
The rolling bearing is a rotating part of the drive motor. High speed, high temperature, frequent start and stop accompanied by impact are the main working conditions of the electric vehicle drive motor. The development of a series of sealed deep groove ball bearings that can adapt to the working conditions can meet the needs of a series of new energy vehicle drive motors such as hybrid buses, pure electric buses, pure electric passenger cars, and pure electric minicars. And has been widely used in the market.
The bearing design of the new energy drive motor takes into account good sealing performance, high temperature performance, low temperature performance, repeated start-stop performance, certain axial impact load and other conditions, optimizes the internal structure of the product, fully considers the bearing material, heat treatment, machining accuracy, grease, installation and other effects on the product, so that the product performance has been greatly improved. The limit speed can reach 1.5 times of the limit speed of conventional bearings.
1 speed
Running speed affects the life of both bearing and grease. Therefore, bearing size, cage type, lubrication method, clearance and seal type must be considered when selecting bearings. At present, the speed of the drive motor for new energy vehicles can reach up to 18,000 RPM, and the dmn value can reach more than 800,000.
2 shaft and housing material
Due to the expansion and contraction of the material, the expansion coefficient should be mainly considered when selecting the material of the shaft and the housing. Heat expansion and cold contraction will directly affect the fit of the shaft and the housing, thus affecting the internal clearance of the bearing. The material of the shaft in the field of drive motor is usually medium carbon steel and tempered, and the shell is usually cast aluminum or aluminum alloy material, which can reduce the overall weight of the motor and greatly improve the heat dissipation speed.
3 Environment In the humid, low temperature, high temperature and a lot of mud, dust environment, sealing and sealing materials are particularly important. Need to consider the impact of seals on the product; It is necessary to prevent the oil leakage from polluting the environmental products, and the leakage of grease will cause the lack of oil in the bearing and affect the service life of the bearing.
4 Temperature
Bearing temperature is one of the main reasons affecting the life of the machine. When the operating temperature difference between the ambient temperature and the bearing temperature is large, the bearing will produce a temperature gradient. If the temperature gradient is large, check the internal clearance of the bearing to avoid unnecessary bearing damage.
5 Cage
New energy vehicle drive motor high-speed bearings using high temperature (≥180℃) engineering plastic cage, medium and low speed bearings using SPCC cage, cage has good high-speed performance and low noise performance.
6 Bearing accuracy
New energy vehicle drive motor bearing accuracy level has reached P6 level, internal parameters can reach P5, with extremely high rotation stability and low noise performance (noise level up to Z3 group).
The rated life of a rolling bearing is defined as the number of revolutions (or the number of hours of operation at a constant speed) that the bearing can reach before the bearing ring and rolling element first show signs of fatigue (peeling or breaking). Laboratory test data and practical experience show that the exact same bearing on the surface will still have different life under the same conditions. In general, the bearing life depends on its operating conditions, but the bearing installation and maintenance procedures will also have a direct impact on the life of the bearing, despite many preventive measures, the bearing will still fail in advance. When this happens, the bearing should be carefully checked to determine the root cause of the failure. Corrective action can only be taken after a root cause analysis is completed. The target life is a life value given by the manufacturer based on the ideal value of load and speed. For example, the minimum life under the maximum allowable load is 5000 hours or one year. Under good operating conditions, the bearing can achieve a longer life than expected by general or traditional life calculation methods. Good operating conditions are achieved when the lubricating oil film can effectively separate the rolling surface (raceway and rolling element), or when surface damage due to contaminants is limited.
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