The hub motor technology is also called as the in-wheel motor technology. The hub motor is an ensemble that inserted motor in the wheel, assembled the tire at the outside of rotor, and fixed stator on the shaft. When the hub motor is powered on , the rotor is relatively moved. Electronic shifter (switching circuit) controls the stator winding energization sequence and time according to the position sensor signal, generating a rotary magnetic field, and drives the rotor to rotate. Its greatest advange is to integrate the power, drive, and brakes into the hub, thus greatly simplifying the mechanical part of the electric vehicle. In this case the mechanical part of the electric vehicle can be greatly simplified.
The hub motor driving system is mainly divided into 2 structural types according to the rotor type of the motor: inner rotor type and outer rotor type. The outer rotor type adopts a low-speed outer transmission motor, the maximum speed of the motor is 1000-1500r/min, no gear device, the wheel speed is same as motor. While the inner rotor type adopts a high-speed inner rotor motor and is equipped with a gearbox with a fixed transmission ratio. In order to obtain a higher power density, the motor speed can be as high as 10000r/min. With the advent of more compact planetary gear gearbox, inner-rotor in-wheel motors are more competitive in power density than low-speed outer-rotor types.
Advantages of hub motor:
1. The application of in-wheel motors can greatly simplify the structure of the vehicle. The traditional clutch, gearbox, and transmission shaft will no longer exist, and a lot of transmission components will be omitted, making the vehicle structure simpler, and the vehicle inside space spacious.
2. A variety of complex driving methods can be realized
Since the hub motor has the characteristics of independent driving of a single wheel, it can be easily implemented whether it is front-wheel drive, rear-wheel drive or four-wheel drive. Full-time four-wheel drive is very easy to implement on a vehicle driven by an in-wheel motor.
Disadvantages of hub motor:
1. Although the quality of the vehicle is greatly reduced, the unsprung quality is greatly improved, which will have a huge impact on the handling, comfort and suspension reliability of the vehicle.
2. The cost issue. The high conversion efficiency, lightweight four-wheel hub motor cost remains high.
3. Reliability problem. Putting the precision motor on the wheel, long-term violent up and down vibration and the failure problem caused by the harsh working environment (water, dust), and considering the wheel hub part is the part that is easily damaged in a car accident, the maintenance costs are high.
4. The braking heat and energy consumption issue. The motor itself is generating heat. Due to the increase in unsprung mass, the braking pressure is greater and the heat generation is also greater. Such concentrated heat generation requires high braking performance.
Post time: Nov-21-2022