New energy commercial vehicle electric drive
In the field of passenger vehicles, new energy vehicles developed earlier and related technologies are relatively mature, so they have been widely used; but in the field of commercial vehicles, new energy vehicles are still in the initial stage of development, and there are still many technologies The problem needs to be studied urgently, and new energy commercial vehicles are mainly used in urban buses and buses, and have not yet been widely popularized. At present, the electric drive axles commonly used in new energy vehicles mainly include: integrated electric drive axles, coaxial electric drive axles and wheel-side electric drive axles, etc.
Basic concept of electric drive system
The electric drive system of modern electric vehicles is mainly composed of four major parts: drive motor, transmission, power converter and controller. The drive motor is the core of the electric drive system, and its performance and efficiency directly affect the performance of electric vehicles. The electric drive system is actually similar to the power system of a fuel vehicle. Its main function is to convert the DC voltage provided by the power battery into a three-phase AC to drive the motor. After deceleration, torque increase and differential speed, it is distributed to the wheels to drive the vehicle. The size and weight of the drive motor and transmission also affect the overall efficiency of the vehicle; power converters and controllers have a lot to do with the safe and reliable operation of electric vehicles.
Basic structure type of electric drive system of existing commercial vehicles
There are many types of commercial vehicles and their uses are different, so the structural types of commercial vehicle electric drive axle assemblies are also diverse. At present, the common commercial electric vehicle powertrain mainly includes the following types:
1. Traditional car modified electric drive assembly
As shown in the figure, the traditional vehicle modified electric drive assembly retains the structural form of the traditional fuel vehicle drive system, replacing the internal combustion engine with a drive motor. The advantage of this electric drive assembly is that it retains most of the structure of the traditional drive axle, so it is less difficult to develop; the disadvantage is that the transmission chain is long and the transmission efficiency of the vehicle is relatively low. In addition, too many transmission parts lead to heavy body weight, and the transmission system takes up a lot of space, which is not convenient for the arrangement of battery packs.
Traditional car modified electric drive assembly
2. Parallel electric drive axle assembly
As shown in the figure, the parallel electric drive axle adopts an integrated integrated structure, and usually does not use a mechanical transmission, eliminating the need for a lengthy transmission chain. The advantages of this electric drive assembly are: generally a fixed reduction ratio is used, and the speed can be directly adjusted by the motor, so the efficiency is high, the development and manufacturing costs are low, and due to the high integration of the electric drive axle, there is enough space for the body It is used to place the battery pack; the disadvantage is that the unsprung weight is relatively large, which is not conducive to handling. Suitable for heavy duty commercial vehicles.
Parallel electric drive axle assembly
3. Coaxial electric drive axle assembly
As shown in the figure, the coaxial electric drive axle arranges the motor and the transmission half shaft coaxially, and the reducer mostly uses a planetary reducer. The advantages of the coaxial electric drive axle are: very high integration and compact structure; the disadvantages are: the development is difficult, and the motor, as a load-bearing part, has high requirements for its strength and rigidity. Suitable for light load environment.
Coaxial electric drive axle assembly
4. Wheel-type electric drive axle assembly
As shown in the figure, the wheel-side electric drive axle is driven by a hub motor. The advantage of this type of drive axle is that the main parts of the axle are concentrated near the hubs on both sides, and there is sufficient space in the middle of the axle to facilitate the arrangement of other components; the disadvantage is that each independent drive wheel needs to be equipped with a set of reducers. As a result, the weight of the driving axle is relatively large, and the development is difficult. Suitable for low-floor buses.
Wheel side electric drive axle assembly
Driving solutions for electric vehicles
1. Differential half shaft drive scheme
The difference between this scheme and the engine drive scheme of traditional cars is that the engine is converted into an electric motor and related electronic devices. The drive is provided by an electric motor, which drives the wheels on both sides of the vehicle. The operation mode of the electric vehicle in this arrangement is the same as that of a traditional vehicle. The motor controller receives signals from the accelerator pedal, etc., and drives the left and right wheels through mechanical transmission. This form retains mechanical components, including transmissions, transmission shafts, and half shafts. The advantage is that the technology is relatively mature, which is conducive to concentrating on matching the power system of electric vehicles; Automotive performance requirements.
2. Wheel drive scheme
The main feature of the wheel-side drive scheme is that the differential and half shafts are canceled, and the planetary reducer and the motor are manufactured as one, which is combined into an electric wheel, and the electric wheel is directly installed on the wheel. This solution integrates the motor, transmission mechanism and brake, and is a unique drive unit; the electric vehicle using electric wheel technology does not occupy the space of the body and chassis, which expands the driving space, and the space at the bottom of the vehicle is used to install the battery. The overall layout of the entire vehicle is greatly simplified, and the vehicle is environmentally friendly and has high transmission efficiency.
3. Hub motor drive scheme
In-wheel motor drive is a hotspot in the research and development of electric vehicles, and it is also an effective means to solve energy and environmental problems. The hub motor is installed in the hub of the wheel, omitting the intermediate mechanical transmission components such as clutch, reducer and transmission bridge. The hub motor drive system of the electric vehicle receives the electric energy of the battery, and the motor directly drives the wheel to drive the electric vehicle, which greatly simplifies The structure of the whole vehicle is improved, and the transmission efficiency is improved. Due to the cancellation of the differential, the control of the torque and speed of the drive motor is the focus of research, and its differential speed control technology directly affects the development of in-wheel motor electric vehicles.
Most of the in-wheel motors of modern cars use permanent magnet materials. With the rapid development of modern control theory, electronic technology and permanent magnet motor optimization design technology, hub motor drive technology has gradually matured and applied in various fields of electric vehicles.
Summarize
With the clarification of the national policy orientation and the active support of the local government, the rapid development of the electric vehicle industry has become an inevitable trend, and will eventually promote the electrification of the automobile industry. With the development trend of vehicle electrification.
