Research on the Wheel Motor Industry: The Ultimate Solution for Electric Vehicle Transmission Systems?
Electric vehicles can be divided into centralized motor drive and distributed motor drive (including wheel edge motor drive and wheel hub motor drive) according to their driving methods. At present, most electric vehicles are driven by centralized motors, and wheel motor drive has begun to be applied in the bus market. Wheel motor drive is still in the research and development stage, but it is the development direction of future electric vehicle drive systems.
Wheel hub motors have the following advantages: (1) High efficiency and energy saving: Wheel hub motors eliminate the need for clutches, transmissions, and other devices, greatly improving transmission efficiency. At the same time, brake energy recovery can be more efficiently achieved in wheel hub motor driven vehicle models, thereby increasing range. (2) Integrated and lightweight: The wheel hub motor integrates power, transmission, and braking into the wheel hub, greatly simplifying the chassis structure and saving interior space, improving the utilization of car space, and reducing its own weight by 30%. (3) Flexible driving: The wheel hub motor directly drives the wheels, and the MCU can control the speed and torque of the wheels with high precision without complex operation instructions, meeting the driving needs under different working conditions. Wheel hub motors can be divided into two types: inner rotors and outer rotors. The inner rotor has a higher rotational speed and is used in conjunction with a reduction device, while the outer rotor has a relatively simple structure and does not require a reduction mechanism.
Japan was one of the earliest to enter the field of wheel hub motor research and development. Since 1991, major universities in Japan have collaborated with industry and research institutions to conduct research on wheel hub motors; At the industrial level, European and American companies dominate, with typical examples including e-Traction from the Netherlands, Protean from the United States, and Elaphe from Europe. Since 2010, major universities in China have been developing wheel hub motor technology, and major transmission system suppliers have begun to introduce advanced foreign technology through mergers and acquisitions. However, there is still a certain distance from industrialization. TaiTe Electromechanical, Wan'an Technology, and Asia Pacific Group have invested in e-Traction Protean、Elaphe。 In 2010, Guangzhou Automobile Group released a traditional pure electric vehicle, and in 2011, Chery released a Ruilin XI-EV that applied wheel hub motors.
Pain points of wheel hub motors: (1) High cost: The cost of small-scale production with distributed drive is about 150% of that with centralized drive. If production scale is achieved, the cost of distributed drive is about 120% of that with centralized drive. (2) The integration of wheel hub motors has resulted in a decrease in spring-loaded mass and an increase in non spring-loaded mass, leading to a decrease in isolation vibration performance and affecting the smoothness and safety of vehicle operation. (3) The problem of heat dissipation and cooling of wheel hub motors needs to be tested: when the vehicle is driving under high load, low-speed climbing conditions, due to limited wheel hub space, insufficient cooling is prone to occur.
