With the expansion of the new energy vehicle market, more and more automobile manufacturers are investing in the research and development of electric motors. Currently, the most mainstream electric motors are placed in the position of the front internal combustion engine of traditional automobiles or on the rear axle. , the layout is no different from traditional cars, but in many concept electric cars, we will see the term in-wheel motor, which is installed on the hub of the wheel and directly drives the wheel. As a new research direction, although there are already many manufacturers in We are committed to this, but we still have not seen large-scale equipment. So what is the difference between in-wheel motors and traditional motors, and what are their advantages and disadvantages? Today our car selection detective will analyze it in detail.
1. Is the principle of in-wheel motor the same as that of traditional motor?
Take the asynchronous hub motor as an example. It is mainly composed of a stator, a rotor and additional parts. The stator core is generally made of silicon steel sheets with an insulating layer and is used to place the stator windings. The stator windings rotate at the same angle. Distributed on the center of the circle, that is, each at an angle of 120 degrees, the coils on the windings are wound according to a certain pattern, and current flows through the stator windings to generate a rotating magnetic field. At this time, the rotating magnetic field and the rotor conductor have relative cutting motion. According to the principle of electromagnetic induction, the rotor conductor generates an induced electromotive force and an induced current. The rotor conductor is acted upon by electromagnetic force in the magnetic field, forming an electromagnetic torque, which drives the rotor to rotate. In layman's terms, it is the process of converting the electrical energy of the current into mechanical energy. I believe many people have played with four-wheel drive vehicles when they were children. The motor that drives the four-wheel drive vehicle is a small motor, but the two magnets inside are permanent magnets, and the AC Motors require electricity to generate a magnetic field. Compared with internal combustion engines, motors are actually simpler and easier to control.
The principle of a hub motor is actually no different from a traditional motor, but it is more compact in structure, which means there are fewer coils, and the magnetic field is not as strong as a motor with a traditional position, so the output power is relatively small. In addition, there are two types of hub motors: internal rotating motors and external rotating motors, where the rotor of the external rotating motor is located inside the stator, just like a traditional motor. The rotor of an external-rotation motor is located outside the stator and rotates around the stator. The in-wheel motor integrates the power unit, transmission device and braking device into the wheel hub, so the mechanical part of the electric vehicle is greatly simplified.
2. What are the advantages and disadvantages of hub motors compared to traditional motors?
As mentioned above, due to the limited diameter of the wheel hub and the limited width of the tire, the maximum volume of the wheel hub motor is not as good as that of the traditional motor, and the output power is also difficult to meet the standard. Therefore, many wheel hub motors are currently only used on two wheels. Used on electric bicycles. Compared with traditional motors, in-wheel motors actually have many very significant advantages. First of all, this design has no transmission losses because there is no transmission rod from the engine to the wheels, so the efficiency is very high. In addition, the wheel hub motor can reverse the different speeds of the left and right wheels to achieve differential steering similar to that of a tracked vehicle, greatly reducing the turning radius of the vehicle. Under special circumstances, it can almost achieve in-situ steering, which is often referred to as tank turning. . In terms of loading space, hub motor vehicles also have an advantage, and they can have spacious luggage boxes at the front and rear.
With so many advantages, why is it difficult to see in reality? In addition to power factors, cost is also a factor that restricts development. Since the brake system also needs to be integrated into the wheel hub, integration is more difficult than traditional motors. High, and the heat dissipation of the braking system is also a very important part. Although the motor does not require too much air to dissipate heat, it will occupy most of the volume, making heat dissipation more difficult and posing brake safety risks.
Secondly, the lifespan is also more expensive than the traditional motor placed in the middle of the vehicle. The motor in the cabin will have multiple protective layers and will not be exposed to wind or sun, while on the road Pebbles and dust will not affect the motor. Because the hub motor is exposed to the outside, its service life is short and it often needs maintenance. These are urgent problems that the hub motor needs to solve.
Car Selection Detective’s View: In daily life, it is currently difficult for us to see mass-produced cars equipped with in-wheel motors, but with the development of electric vehicles, I believe there will be such electric vehicles in the near future However, due to the obvious shortcomings, although there are new breakthroughs in control, maintenance is the biggest problem, so we do not recommend choosing this type of model.
This article comes from the author of Autohome Chejiahao and does not represent the views and positions of Autohome.