Edited by Asiautos Auto Part
The hub motor eliminates mechanical connections such as the drive shaft, half shaft, and steering knuckle, simplifies the transmission system, significantly improves transmission efficiency, and saves chassis space. The development history of hub motors has mainly gone through three stages: origin, breakthrough and application. The concept of hub motors can be traced back to around 1890, when the first patents for direct-drive and reduction hub motors appeared.
In 1900, Dr. Ferdinand Porsche successfully built the first hub motor-driven car. Although he successively manufactured two-wheel drive, four-wheel drive and hybrid configurations, the hub motor drive technology was not promoted due to the immaturity of the three-electric technology.
In 1940, wheel hub motors were used in large special vehicles such as mining trucks. In the past 20 years, wheel hub motors have been initially applied in pickup trucks and cars, proving that they have great potential in distributed control and efficiency. The main obstacle to their application is the premise of ensuring the torque output capacity and energy conversion efficiency of wheel hub motors. Reducing weight and volume means increasing torque density.

1. Key technologies of hub motors
Overall configuration
The requirements of various types of vehicles vary greatly, and different requirements are put forward for the torque, space and quality of hub motors, which has led to the development of the overall configuration scheme of hub motors. Whether to use a reducer to increase the output torque is an important factor affecting the design of hub motors. Hub motors are divided into direct drive and deceleration drive according to whether the overall configuration uses a reducer.
The direct drive configuration rigidly connects the hub motor rotor with the hub bearing or rim, and has the characteristics of simple structure, small size and light weight. Deceleration drive includes three types of configurations: multi-stage deceleration, single-stage deceleration, and speed change mechanism. This type of configuration amplifies the torque generated by the hub motor through a parallel shaft reducer and a planetary gear reducer and then transmits it to the wheel hub.
The overall configuration of the hub motor is a key factor in determining the torque density of the hub motor. The difference in the overall configuration has led to a shift in the application scenarios of the hub motor. Compared with the mainstream centralized drive (high-speed motor reducer), the hub motor drive mode is more diverse, but the relationship between the overall configuration of the hub motor and the application scenario has not yet been fully clarified.
Electromagnetic topology
Electromagnetic topology is a key factor affecting the torque output capacity, energy conversion efficiency, and electromagnetic effective mass of the hub motor. The diverse overall configuration of the hub motor leads to flexible design of its electromagnetic structure topology.
the hub motor is divided into an outer rotor-inner stator topology, an inner rotor-outer stator topology, and a multi-rotor or multi-stator topology according to the topological relationship between the stator and the rotor. The inner rotor and outer stator motor has been used in direct drive and reduction drive hub motors. 11Surface mount and built-in are typical topological structures of inner rotor hub motors. The surface mount type has excellent performance in the low speed area, while the built-in type has excellent overload capacity and low loss in the high speed area.
Therefore, the built-in permanent magnet synchronous motor is more suitable for the reduction drive hub motor configuration. The outer rotor and inner stator motor provides a larger permanent magnet arrangement space and higher torque output capacity. Among them, compared with the built-in type, the surface mount hub motor has a higher output torque, but its direct axis and quadrature axis inductance are similar, and the reluctance torque cannot be fully utilized.
Multi-rotor or multi-stator wheel hub motors mainly include magnetic field modulation motors and compound magnetic field motors. In magnetic field modulation motors, the output torque is amplified by adding a modulation ring between the stator and the rotor. Compound magnetic field motors increase the number of air gaps inside the motor and can output greater torque and power. The working principle of the wheel hub motor is similar to that of the centralized drive motor, but increasing the output power of the wheel hub motor does not rely on increasing the speed, but directly increasing the density by optimizing the electromagnetic topology.
Heat dissipation method
The heat dissipation scheme determines the duration of the motor torque and indirectly affects the torque density of the hub motor, showing the multi-physics field coupling characteristics. The specific heat dissipation forms of the hub motor mainly include air cooling, water cooling and oil cooling.
Determining the overall configuration and electromagnetic topology of the hub motor is the premise of heat dissipation design. The air cooling heat dissipation method uses the wind from the hub to directly transfer the internal heat of the motor to the environment by designing a reasonable heat sink shape, and has the characteristics of high reliability and simple structure. However, the heat dissipation capacity of air cooling is limited, and it is usually used for hub motors with a power of less than 20kW. In the heat dissipation scheme, water cooling has a larger heat dissipation power.
Its heat dissipation effect depends on the shape and layout of the water jacket. The water jacket can be U-shaped or spiral. The optimized water cooling system can be used to cool a 100kW hub motor. Using lubricating oil as a coolant can simultaneously lubricate and cool the hub motor and reducer. Multiple cooling methods can be used in combination to improve the cooling capacity of the hub motor heat dissipation system.
2. Advances in wheel hub motor technology
The iteration of wheel hub motor products has promoted its technological progress. To ensure the reliability of wheel hub motor products, Protean proposed a high-safety design concept for sub-motors. In order to improve the torque density of wheel hub motors, Elaphe studied the method of high permanent magnet utilization.
Schaeffler and NTN took advantage of the technical advantages of automotive parts and launched inner rotor wheel hub motor products, expanding the application range of wheel hub motors. The torque density of wheel hub motors can be divided into mass torque density and volume torque density. The latter is an important indicator for the comparison of direct-drive wheel hub motors, while the volume torque density does not fully consider the influence of in-wheel structural parts and reducers. Therefore, this review emphasizes mass torque density.
At present, limited torque density hinders the widespread application of wheel hub motors. The differences in the performance requirements of wheel hub motors in different application scenarios lead to different difficulties in promoting wheel hub motor solutions on different models. To accelerate the application of hub motors, first, the proportion of hub motors installed in special vehicles (airport vehicles) and heavy vehicles (mining trucks) should be increased, and the hub motors should be further integrated with the hub structure; second, lightweight hub motor drive solutions should be designed for self-driving cars and other low-speed vehicles; finally, the application scenarios should be gradually expanded from heavy and light vehicles to high-end passenger cars and pickup trucks.
3. Development Prospects of Hub Motors
The future development trends of hub motors include new material applications, design optimization and structural integration. New materials will expand the performance boundaries, intelligent optimization methods will find the optimal design, and structural integration will achieve functional innovation of hubs and motors. The main materials of hub motors are copper, permanent magnets, electrical steel and aluminum, among which copper and permanent magnets have a greater impact on their performance. In terms of conductor materials, carbon-based composites have made good progress at the laboratory level. The main application difficulty lies in how to ensure the overall conductivity of the material at a large scale. In terms of permanent magnets, since hub motors require permanent magnets to have the characteristics of high magnetic energy product, demagnetization resistance and easy bonding, material modification is difficult to meet the above requirements at the same time. Therefore, arranging permanent magnets of different materials in different regions to form composite permanent magnets is expected to improve the comprehensive performance of permanent magnets.
The intelligent optimization design of hub motors is a complex nonlinear problem involving the construction of proxy models and the optimization of design parameters. In order to avoid the problems of limited modeling accuracy of analytical methods and large calculation amount of finite element models, artificial intelligence algorithms are widely used in the optimization of hub motor design parameters. However, in fact, the performance boundary of parameter optimization is constrained by the geometric template. Further optimization of the hub motor topology can expand the parameter optimization boundary and achieve efficient material utilization.

C00014551 |
C00014611 |
C00090138 |
C00014621 |
C00217154 |
C00229941 |
C00077430 |
C00079038 |
C00079036 |
C00014631 |
C00014620 |
C00014662 |
C00108625 |
C00079178 |
C00077423 |
C00238689 |
C00077409 |
C00079109 |
C00047999 |
C00014631 |
C00217169 |
C00216475 |
C00075679 |
C00079034 |
C00111121 |
C00112937 |
C00014558 |
C00014548 |
C00100381 |
C00180866 |
C00072270 |
C00199629 |
C00095465 |
C00030523 |
C00014563 |
C00111120 |
C00014648 |
C00112938 |
C00260664 |
C00238707 |
C00014619 |
C00033625 |
C00014648 |
C00046499 |
C00001531 |
C00079184 |
C00108625 |
ILZKAR8G8 |
C00087169 |
C00076630 |
C00180866 |
C00105550 |
C00080545 |
F01R00A053 10163098 |
C00232562 |
C00076661 |
C00120693 |
C00105548 |
C00185657 |
C00308847 |
C00074778 |
C00215065 |
C00334135 |
C00111120 |
C00310876/230883 |
C00271216-B |
C00075902 |
C00076977 |
C00079034 |
C00081098 |
C00230356 |
C00217154 C00229941 |
C00211246 |
C00076978 |
C00076423 |
C00075314/384459 |
C00105783 |
C00216475 |
C00185606 |
C00085855 |
C00076424 |
C00166467/399203 |
C00105782 |
C00137817 |
C00185605 |
C00085856 |
C00076421 |
C00074269 |
C00085859/361295 |
C00100328 |
C00110052 |
C00238349 |
C00076422 |
C00074267 |
C00211378/361363 |
C00090138 |
C00084280 |
C00238348 |
C00076611 |
C00074268 |
C00097788 |
C00027011 |
C00308847 |
C00024453 |
C00049964 |
C00027004 |
C00027215 |
C00024454 |
C00049880 |
C00070955 |
C00040700 |
C00243826 |
C00056865-4100 |
C00025946 |
10048015-RED |
C00020636 |
C00037057 |
C00071771 |
10048016-RED |
C00039611 |
C00037058 |
C00027620 |
10048029 |
C00056866-4100 |
C00367229 |
C00033318 |
10061458-BLU |
C00042395 |
C00126306 |
C00027617 |
10048010-B |
C00039529 |
C00228359 |
C00027622 |
C00074649 |
C00019173 |
C00030763 |
C00027619 |
C00016823 |
C00056664 |
10048084 |
ASIAUTOS.NET
Your reliable supply partner for China Car auto parts