First of all, the integration of the wheel hub and the motor undoubtedly increases the unsprung quality, which greatly reduces the comfort and handling of the whole vehicle. This is the same as the shoes we wear. If the shoes are too heavy, it will be inconvenient to walk and slow to react.

Secondly, the heat dissipation of hub motor is difficult. Because the hub motor is integrated in the hub, the heat dissipation environment is poor, which is easy to cause the motor to overheat and affect the service life of the motor. In addition, the heat generated by wheel friction and the heat generated by the motor are easy to cause tire damage.

Third, the environmental adaptability of hub motor is poor. Because the hub motor is integrated in the hub, the ground clearance is relatively low, so it is more vulnerable to impact or damage when encountering rain, snow, gravel, muddy road or wading road.

Fourth, demagnetization of permanent magnet materials. Hub motor is generally surface mounted rotor structure, and the magnetic steel directly faces the air gap magnetic field, which is easy to demagnetize. To improve this problem, we need to learn from the development path of centralized motor. It is the transition from surface mounted rotor structure to interpolation rotor structure, from single-layer structure to double-layer structure. After the magnetic steel is embedded in the iron core, the iron core can bypass the demagnetizing magnetic field and prevent the permanent magnet from directly facing the demagnetizing magnetic field.

Fifth, the space in the wheel is limited, and the motor is difficult to do very much, resulting in great restrictions on power and torque.

Sixth, cost. From the perspective of research, hub motor makes people very optimistic about the development of driving technology in the future. However, due to its high cost, the large-scale commercial application of hub motor driving technology has not been realized. In the front or rear wheels of the vehicle, the hub motors are carried in pairs, even in more axles with more than four wheels, and each hub motor usually adopts an independent electric control system. Therefore, under the same power output conditions, if the vehicle power system adopts the hub motor drive scheme, the price and cost will be several times that of the central motor drive scheme.

Seventh, industrialization. The road of hub motor industrialization must be supported by the synchronous engineering of the upstream and downstream industrial chain, develop their strengths and solve the difficulties such as technology and cost. The professional parts supplier of hub motor needs to continue to cooperate with the sample development and establish a stable supply capacity within 3 ~ 5 years to break the monopoly of foreign intellectual property rights; Vehicle manufacturers promote the research and development of a new generation of vehicle chassis dynamics integrated control system such as low floor type, integrate the functions of braking / driving, steering and active suspension into the "driving wheel" or "electric wheel", and improve the commercial value of new energy vehicles such as fuel cells and electric vehicles in terms of available interior space, range, intelligent driving and handling safety; Improving the vehicle experience and product sales service system of ordinary end customers has a great impact on the progress of industrialization promotion.

Original link: https://mp.weixin.qq.com/s/RMA_vdE37PcVlufdShW5Dg