What is the structural form of hub motor? What are the characteristics of its drive system?

According to the rotor type of the motor, the hub motor drive system is mainly divided into two structural types: inner rotor type and outer rotor type.

Inner rotor type: high-speed inner rotor motor with fixed transmission ratio reducer. In order to obtain higher power density, the speed of the motor can be as high as 10000 rpm. With the appearance of more compact planetary gear reducer, the inner rotor hub motor is more competitive than the low-speed outer rotor motor in power density.

Outer rotor type: low-speed outer rotor motor is adopted, with the highest speed of 1000- 1500r/min, without reducer, and the wheel speed is consistent with the motor speed;

Second, the characteristics of the hub motor drive system

① The hub motor is directly installed on the hub to drive the vehicle. Vehicles do not need to be equipped with clutches, gearboxes, transmission shafts, differentials or even gearboxes. The rear floor protrusion of traditional rear wheel drive will disappear in electric vehicles, providing more space for passengers and improving the space utilization and transmission efficiency of vehicles. Reduce the failure rate of regular maintenance and operation.

Advantages: flexible configuration and easy realization of multiple driving modes.

② The hub motor independently drives one wheel, which can easily realize front-drive, rear-drive or four-wheel drive, even differential or left-right twisting, greatly improving the driving performance of the vehicle.

Advantages: it is convenient to match various new energy technologies.

Whether it is pure electric vehicle, hybrid electric vehicle or fuel cell electric vehicle, the power battery is basically used to provide electric energy, which can be seamlessly connected with the hub motor and can well accept the energy recovered by braking. Although there are some objective facts such as the increase of unsprung weight, the large moment of inertia of the hub and the complicated coordination of the control system, with the progress of technology, we have reason to believe that it will be solved soon and will no longer be the bottleneck of application.

The working ring of motor hub is not good, which is affected by water and dust, and requires high sealing performance. In addition, how to realize the electric braking scheme and how to dissipate heat also need to be studied and solved. Although in-wheel motor technology still faces many challenges, successful examples are not uncommon. The West Lake BYD K9 electric bus representing domestic cars has been exported to Europe and America. The technology adopted is wheel-side deceleration hub motor technology. With the maturity and innovation of technology, the technology is gradually applied to SUVs and family cars.