In-wheel motor technology, also known as wheel-mounted motor technology, is characterized by integrating the power, transmission, and braking systems into the wheel hub, thus greatly simplifying the mechanical components of electric vehicles. In-wheel motor technology is not new; electric vehicles equipped with in-wheel motors on the front wheels were manufactured as early as 1900, and this technology was applied in fields such as mining vehicles in the 1970s. For in-wheel motors used in passenger vehicles, Japanese manufacturers began research and development earlier and currently hold a leading position. International automotive giants, including GM and Toyota, have also ventured into this technology.
Structure of hub motor
Hub motor drive systems are mainly divided into two structural types based on the rotor type: internal rotor and external rotor. The external rotor type uses a low-speed external rotor motor with a maximum speed of 1000-1500 r/min, without a reduction gear; the wheel speed is the same as the motor speed. The internal rotor type, on the other hand, uses a high-speed internal rotor motor equipped with a fixed-ratio reducer. To achieve higher power density, the motor speed can reach up to 10000 r/min. With the advent of more compact planetary gear reducers, internal rotor hub motors are more competitive in terms of power density than low-speed external rotor motors.
Working principle of hub motor
The working principle of the hub motor of an electric vehicle is: electronic commutator (switching circuit).
Based on the position sensor signal, the energizing sequence and timing of the stator windings are controlled to generate a rotating magnetic field, which drives the rotor to rotate.
The wheel hub motor assembly and control system of electric vehicles are automotive parts and are key core components of electric vehicles.
The system is characterized by its unique design that integrates the motor system, braking system, and suspension system. It features permanent magnet brushless synchronous electric vehicle hub motors and switched reluctance hub motors, and can be controlled by PWM and AC frequency conversion. This comprehensive product design is characterized by high efficiency, light weight, long life, low noise, strong matching, simple structure, easy assembly, full functionality, independent suspension, and safety and reliability. It does not require mechanical components such as axles and gearboxes, but directly suspends the tires on the vehicle body, resulting in zero transmission loss and 100% rotational efficiency.
Compared to traditional electric vehicle mechanical transmission systems such as motor drive shaft-gearbox-differential-axle, this system represents a qualitative change. As a result, its overall structure, driving performance, comprehensive efficiency, and driving range are superior to any other type of drive structure. It can be configured as two-wheel drive or four-wheel drive, making it the preferred drive system for electric vehicles. Moreover, it can be matched with any type of vehicle to form a hybrid electric vehicle. In-wheel motor drive is the future development direction of electric vehicle drive systems.
