A hub motor is a permanent magnet DC motor that combines a motor and a wheel. Hub motor technology, also known as in-wheel motor technology, is characterized by the integration of power, transmission and braking devices into the wheel hub, thus greatly simplifying the mechanical part of the electric vehicle. Hub motor technology is not a new thing, as early as 1900, the front wheels have been manufactured and equipped with hub motor electric vehicles, in the 1970s, and this technology is in the field of mining transport vehicles and other applications.
The hub motor power system usually consists of a motor, reduction mechanism, brake and heat dissipation system, etc. The hub motor drive system is mainly divided into two structural types according to the rotor type of the motor: inner rotor type and outer rotor type. The outer rotor type uses a low-speed outer rotor motor with a maximum speed of 1000-1500r/min, no reduction device, and the wheel speed is the same as the motor. With the advent of planetary gear reducer, the inner rotor type wheel motor is more competitive than the low-speed outer rotor type in terms of power density.
There are many ways to classify hub motors, and depending on the classification method, they can be divided into different types and application scenarios.
Wheel hub motors can be classified into four categories according to motor type: brushless gearless motors, brushless gearless motors, brushed gearless and brushed gearless motors. Brushless gear motors are mainly used in industries with low-speed requirements and certain torque requirements. The toothless motor in the market has been difficult to see, mostly belongs to the inner rotor motor, does not belong to the wheel grain motor category. Brushed and toothed motors are mainly used in wheelchair vehicles. Brushless gearless motor is the most common type of wheeled grain motor, mainly used in balance vehicles, scooters, electric vehicles, Harley bikes and other modified vehicles.
According to the way of output shaft, it is divided into two-shaft motor and single-shaft motor. Single-axis motors are mainly used in three-wheeled vehicles or four-wheeled dual-drive conversion vehicles. Single shaft motors are used in the common electric two-wheelers in the market.
According to the use of the nomenclature on the size can be divided into scooter motor (cart, wheelchair), riding motor, rear axle motor.
The use of hub motors not only eliminates a large number of transmission components, making the vehicle structure simpler, but also allows for a variety of complex drive options. For conventional vehicles, clutch, transmission, drive shaft and other components are essential, but these components make the structure of the vehicle more complex and increase the weight of the machine. But hub motors are a good solution to this problem. As the hub motor has the characteristics of single wheel independent drive, so whether it is front drive, rear drive or four-wheel drive form, it can be relatively easy to achieve, full-time four-wheel drive in the vehicle driven by the hub motor is also very easy to achieve.
Increasing the unsprung mass and rotational inertia of the wheel has an impact on the handling of the vehicle. Common civilian vehicles often use relatively lightweight materials for suspension components to reduce unsprung mass and improve suspension response. However, hub motors increase the unsprung mass and also increase the rotational inertia of the hub, which is detrimental to the vehicle's handling performance. However, considering that electric vehicles are mostly limited to transportation rather than power performance, this is not the biggest flaw yet. The high conversion efficiency and light weight of the hub motor itself also make the cost of the hub motor high.
Hub motor technology does have very good advantages, not only can save a lot of space, but also can improve transmission efficiency, is a very good direction for the development of new energy vehicles. But with the current level of development, there are still some problems, but of course, this does not affect the hub motor is still a very promising product.
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