In the era of new energy, electric vehicles have become the darling of the market, and the driving form of electric vehicles is not single. One of them is the wheel hub motor, which has promising prospects but is difficult to popularize at present.
In fact, the wheel hub motor is very common. Electric bicycles are driven by this type of driving mode, which integrates the motor into the inside of the wheel and sounds like a perfect driving solution. The working principle of the wheel hub motor is a permanent magnet synchronous motor, and the edge motor and wheel hub motor refer to motors installed in different positions on the vehicle. The wheel hub motor is designed to integrate the "power system, transmission system, and brake system" of the vehicle together. Because the wheel hub motor has the characteristic of independent driving of a single wheel, it can be relatively easily achieved in front-wheel drive, rear-wheel drive or four-wheel drive forms, and all-wheel drive can be easily achieved in vehicles driven by wheel hub motors.
Bearing and driving
Bearing and driving are necessary functions of the electric wheel hub motor. The implementation of bearing relies on the axle bearing to realize the centering of the rotor and the stator. The wheel rim of the vehicle passes through the axle bearing instead of being connected to the suspension bridge by the stator and rotor to bear the shock absorber and load of the road surface. The driving method is to connect the external rotor directly with the wheel rim to achieve direct driving.
Electronic differential control
Electronic differential control is also one of the functions of the wheel hub motor. The implementation method is that the front wheels turn, which is completed by the ordinary steering gear; the rear wheel needs to turn differentially, which is completed by the electronic differential; the turning radius is determined by the turning angle of the front steering gear, and the turning differential of the rear wheel is determined by the turning radius and wheelbase of the vehicle. By calculating the turning angle of the front steering gear, the turning differential of the rear wheel is calculated. The steering gear can also be electronic steering. Even if the rear wheel cannot strictly differential, the inner wheel should change from "active" to "passive" by disconnecting the motor or serially connecting compensating resistors in the circuit.
Brake energy recovery
The function of the wheel hub motor also includes brake energy recovery. During the braking process of an electric vehicle, the vehicle's kinetic energy is transmitted to the motor through the wheels, thereby driving the motor to rotate. At this time, the motor is operating in a power generation state, charging the energy storage device, which is the battery or supercapacitor, and converting the braking energy into electrical energy stored in the energy storage device for regeneration and reuse. At the same time, the resistance torque generated by the motor acts on the wheel, producing a braking torque and playing a role in deceleration and braking. There are two cooling methods for the motor: air cooling and water cooling. Air cooling uses a structure that is beneficial to gas circulation to cool the wheel hub motor, such as an integrated cooling fan; water cooling sets a dedicated cooling liquid channel and cools the wheel hub motor through heat exchange with the liquid.