Increase the unsprung mass and the moment of inertia of the hub, which has an impact on the handling of the vehicle
For ordinary civilian vehicles, some relatively lightweight materials such as aluminum alloys are often used to make the suspended components to reduce the unsprung mass and improve the response speed of the suspension. However, the hub motor just increases the unsprung mass to a large extent, and also increases the moment of inertia of the hub, which is detrimental to the handling performance of the vehicle. However, considering that electric vehicles are mostly limited to travel rather than pursuing power performance, this is not the biggest flaw.
Electric braking performance is limited, and it takes a lot of power to maintain the braking system.
Many of today's conventional power commercial vehicles have been equipped with auxiliary reduction gears that utilize the principle of eddy current braking (ie, resistance braking), such as electric retarders used in many trucks. Due to the relationship between energy and electric vehicles, electric braking is also the first choice. However, for the vehicle driven by the hub motor, because the electric braking capacity of the hub motor system is small and cannot meet the requirements of the braking performance of the whole vehicle, additional mechanical system is required. Dynamic system, but for ordinary electric passenger cars, without the vacuum pump driven by the traditional internal combustion engine, the electric vacuum pump is needed to provide the brake boost, but it means that there is more energy consumption, even if the regenerative braking can recover some energy, If the effectiveness of the braking system is to be ensured, the energy consumed by the braking system is also one of the important factors affecting the cruising range of the electric vehicle.
In addition, the working environment of the hub motor is harsh, facing the influence of water, dust, etc., and also has high requirements in terms of sealing. At the same time, it is also necessary to separately consider the heat dissipation problem for the hub motor.