Foreword
In recent years, the greenhouse effect has intensified, and public environmental awareness has steadily increased. Vehicle exhaust emissions are a primary contributor to the urban greenhouse effect; consequently, the development of new energy motorcycles is crucial for addressing exhaust-related pollution. Bearings are vital components of these motorcycles, and their performance directly determines the vehicle's comfort and safety.
The market for new energy motorcycle bearings is projected to reach 34.2 billion yuan by 2028, encompassing components such as drive motor bearings, wheel hub bearing units, transmission bearings, and steering system bearings. Among these, drive motor bearings are essential for providing propulsion. Given the demanding operating conditions involved, performance requirements for these bearings are becoming increasingly stringent, making the development of high-performance drive motor bearings a key focus for major motorcycle and bearing manufacturers.
Structural Characteristics of Drive Motor Bearings for New Energy Motorcycles
The requirements for bearings in new energy motorcycles include long service life, creep resistance, high rotational speed, low friction, and low vibration. Specifically, these manifest as:
(1) High Speed: The drive motor operates at speeds up to 20,000 rpm, with a bearing DmN value (product of mean diameter and rotational speed) exceeding 800,000-significantly higher than that of standard industrial motors.
(2) High Temperature: Bearings must operate stably within a range of -40°C to 150°C without squealing; the long-term operating temperature is 110°C–120°C; cold-start capability is required at -30°C to -20°C, featuring low starting torque and low noise.
(3) Lubrication: Grease requirements include excellent low-temperature performance, high-temperature resistance, vibration resistance, energy efficiency, and long service life.
(4) Vibration and Noise: To ensure rider comfort, the motor must exhibit low vibration and noise levels, ensuring quiet operation of the motorcycle.
(5) Electrical Erosion: Potential differences between rotor components caused by winding imbalances can generate currents; additionally, leakage currents resulting from high-frequency inverter voltages can cause electrical erosion, leading to bearing failure.
(6) Service Life: The bearing lifespan must match the vehicle's warranty period (5–8 years or 100,000–160,000 km).
Current Global Research Status of Bearings for New Energy Motorcycles
Current Status of International Research：
NTN has developed an insulated, electrically corrosion-resistant bearing for electric vehicle (EV) drive systems (e-Axles). By applying an insulating coating to the outer diameter and end faces of the outer ring, the bearing achieves excellent insulation properties and can withstand voltages exceeding 100 V.
NTN also developed an anti-electrolytic corrosion bearing-specifically an insulated bearing for EV axles-designed to suppress current flow through the bearing via a surface coating. This bearing supports high-voltage battery systems, offering insulation capabilities above 100 V. The coating features a low friction coefficient and superior wear resistance; compared to standard non-insulated bearings, the total wear on the outer ring's outer diameter and the housing's inner diameter is reduced by 88%. Consequently, the bearing retains the necessary insulation coating even if outer ring creep occurs.
SKF has launched the HSBB1.8, a revolutionary high-speed deep groove ball bearing for electric drive systems. It achieves a maximum Dmn value of 1.8 million, enabling motor speeds of up to 30,000 rpm for a 40 mm shaft diameter.
NSK has developed a new generation of anti-creep bearings for drive systems, such as those in hybrid and electric vehicle transmissions, aiming to improve ride comfort by suppressing creep. Key features of the product include:
① Prevention of ring deformation through optimized rigidity, minimizing the increase in wall thickness while effectively enhancing resistance to creep caused by static gear loads.
② Use of O-ring material with superior durability in high-temperature oil environments and optimized compression deformation; this reduces creep caused by rotational loads (resulting from motor imbalance) by 80% when the bearing is exposed to high-temperature oil.
③ Enhanced anti-creep performance without the need for mechanical fixation, simplifying assembly and thereby increasing productivity while reducing costs.
Current Status of Domestic Research on Bearings for New Energy Motorcycles：
BLH Bearings has developed a high-speed 2RS series bearing specifically for the drive motors of new energy motorcycles. By employing new designs, manufacturing processes, and materials-and optimizing internal structures through simulation and advanced lubrication technologies-the company has overcome challenges related to heat generation and lubrication under high-speed, high-temperature conditions. This initiative has established design theories and methodologies that ensure the bearings feature high precision, low centrifugal force, and minimal friction, thereby meeting the rigorous demands of new energy motorcycles, including low starting torque, high-speed operation, rapid speed fluctuations, durability, and high reliability.
Dongguan Lihao Bearing Co., Ltd. developed the 6000-2RZU drive motor bearing. Through optimized designs for the bearing rings and cages, the use of non-contact seals, and the application of long-life, low-noise grease capable of withstanding extreme temperatures, the company achieved a design that supports high-speed, high-temperature, and long-life operation. These features enhance stability and noise reduction, ensuring the bearing's longevity and performance during high-speed operation and rapid speed changes.
Guizhou Wanxia Bearing Co., Ltd. has achieved significant breakthroughs in key technologies for bearings used in new energy motorcycle reduction gears, drive motors, and specialized wheel hub units. Notably, regarding wheel hub bearing units for new energy electric vehicles, Wanxia Bearing successfully resolved challenges associated with balancing rigidity and strength in lightweight designs, maintaining dynamic balance after weight reduction, and addressing manufacturing issues caused by deformation in lightweight components; these efforts resulted in a 30% reduction in product weight.
Key Technologies for Xinyuan Motorcycle Bearings
High-speed technology
Achieving high-speed performance is a key challenge in the development of bearings for drive motors in new energy motorcycles, and domestic manufacturers lack directly applicable precedents. To ensure reliability and durability under high-speed conditions, products must not only meet high-speed performance targets in design and theoretical calculations but also pass high-speed performance tests, bench simulation tests, and road trials. Consequently, product development is a complex, long-term undertaking spanning multiple disciplines; achieving industrialization requires balancing cost-effectiveness with performance while overcoming competition from international brands.
Bearing designs must be optimized to minimize friction and wear while maintaining stability during high-speed operation. Specific measures include:
① Grease optimization: Developing high-speed bearings lubricated with grease specifically formulated for drive motors.
② Cage shape optimization: Utilizing steel cages and crown-shaped resin cages for deep-groove ball bearings. Crown-shaped resin cages are lighter than steel cages, resulting in lower centrifugal forces during high-speed rotation and a lower coefficient of friction between the steel balls and the cage pockets, thereby reducing heat generation at the ball-cage interface.
③ Use of high-rigidity resin materials: Resin cage materials intended for high-speed rotation must possess high rigidity to limit deformation caused by centrifugal forces.
High-temperature bearing technology
Due to the thermal effects of electric motors and power electronics, bearings in new energy motorcycles operate at higher temperatures than those in traditional industrial applications-levels comparable to those found in automotive bearings. This necessitates bearing materials capable of withstanding elevated operating temperatures without compromising performance. Specialized alloys, ceramics, and surface coating technologies offer viable solutions for manufacturing bearings that meet the requirements of new energy vehicles, as these materials provide superior wear resistance, corrosion resistance, and thermal stability.
Bearing Corrosion Resistance Technology
With the development of the new energy motorcycle industry, the issue of corrosion in drive motor bearings has increasingly attracted attention. Bearings are critical components of the powertrain; corrosion can compromise vehicle stability and ultimately lead to safety hazards. Specific countermeasures include:
① Optimizing bearing structure, such as enhancing sealing and using corrosion-resistant lubricants.
② Utilizing high-performance, corrosion-resistant materials-such as specialty materials-and employing advanced processing techniques to boost corrosion resistance.
③ Improving bearing lubrication, such as enhancing lubrication between components and using highly corrosion-resistant lubricants.
④ Conducting regular maintenance and inspections of the bearings.
Summarize
The market for traditional motorcycle bearings is facing a major shake-up. As future electric motorcycles utilize electric powertrains-eliminating components such as internal combustion engines, transmissions, and drive shafts-specific bearing products (including those for generators, water pumps, rocker arms, and tensioner pulleys) will undergo significant market restructuring. At the same time, bearings for new energy motorcycles present both new business opportunities and challenges for bearing manufacturers.
