With the development of modern automotive electronic technology, the emergence of new energy vehicles and electric vehicles has undoubtedly injected a fresh and challenging blood into the entire industry. With the ability to reduce the emission of a lot of waste and harmful gases, it has a great improvement effect on the living environment of the entire society, has been highly valued by the society and the country, and has a good development prospect. Let's introduce the electric vehicle transmission system from the structure of the electric vehicle, and analyze its working principle, transmission mode, advantages, etc., and briefly list some successful application cases.

Electric vehicles are different from ordinary cars. They use on-board power to provide driving power and use motors to drive the movement of the wheels, rather than using ignition devices to provide forward movement. We know that electric vehicles are mainly composed of various parts such as electric drive and control system, driving force transmission system, and working device. Its working principle is to provide a constant current output in the battery. These constant circuits are converted into appropriate current and voltage that can drive the motor through the power regulator, so as to drive the normal operation of the entire power transmission system. After their interaction, they finally provide the car with power to run normally.

It can be seen that the effectiveness and safety of the electric vehicle transmission system directly affect the operation of the entire system.

The principle of the electric vehicle transmission system is to directly transmit the driving torque of the motor to the drive shaft of the vehicle. When the vehicle drive shaft is driven by an electric wheel, it can be started with load without a clutch because it is powered by the on-board power supply to drive the motor. It is also because the on-board power supply can provide a constant current, and there will be a circuit control environment in the middle to control the direction and speed of the drive motor, so there is no need for a reverse gear and a differential. If stepless speed regulation is used, automatic control can be achieved without a transmission.

There are three main transmission modes of electric vehicle transmission systems:

(1) Motor + transmission shaft + rear axle

(2) Motor + gearbox + rear axle

(3) Motor + magnetic torque converter + rear axle

In terms of the current maturity of gearbox technology, there is no truly mature product suitable for electric vehicles except for the gearbox of traditional vehicles. The most reliable and applicable transmission mode is the direct drive solution of motor + transmission shaft + rear axle. Of course, in the specific design, we need to design more realistically, including the location of the motor, the location of the power supply, the ability to drive the load, the driving speed requirements, stability, etc. These all need to be considered comprehensively. Understand the distribution of vehicle efficiency losses, that is, the amount and proportion of power consumed by the engine output on different vehicle components. This is very useful for improving the overall transmission efficiency of the vehicle, so as to achieve the purpose of properly allocating resources and improving performance. Various losses are measured using sensors installed at appropriate locations on the vehicle.

Design of topological architecture of electric vehicle transmission system

The vehicle power transmission system uses traditional internal combustion engines and electric motors as power sources, and drives the vehicle by mixing thermal energy and electrical energy. When running at low speed and low power, the engine can be turned off and driven by electric motors; while when driving at high speed, the internal combustion engine is used to drive; through the coordinated working mode of the engine and the electric motor, the energy generated by the vehicle during braking is converted into electrical energy and accumulated as new driving force. Thus, high efficiency can be achieved under different working conditions. Generally, there are four types of layout: series, parallel, hybrid and composite.

(1) Series - The power electronic device used in the figure below is only the motor controller. The battery and auxiliary power unit are directly connected to the inlet of the motor controller. It belongs to the series type, and the driving force of the vehicle comes only from the motor.

(2) Parallel type - The figure below shows a typical parallel power system structure. Usually, a DC/DC converter is installed between the battery and the motor controller. The terminal voltage of the battery is matched with the voltage level of the system DC bus through the boost or buck of the DC/DC converter. The driving force of the vehicle is supplied by the motor and the engine simultaneously or separately.

(3) Hybrid type: It uses four-wheel drive, and the front and rear wheels are connected to different drive systems. The rear wheel drive consists of an engine, a rear motor, a generator, a transmission, etc., and the front wheel drive consists of a front motor and a generator. Because it uses different drive methods, the entire electric vehicle transmission system is both separated and related, which can be better controlled. The figure below is a simple hybrid topology. It has both series and parallel drive modes.

(4) Composite type --- The modified structure is mainly concentrated in the dual-axle hybrid system. The front and rear axles are driven independently, and there is no drive pumping or power active design between the front and rear wheels. This independent drive allows the various components of the transmission system to be independently controlled during operation, so it can have better transmission capacity.

In order to make the entire system run better, in addition to the structural design, another thing is that the parameter design of the electric vehicle transmission system also needs to be reasonably matched. These parameters also have a great impact on the performance of the transmission structure. The editor will not introduce this aspect of knowledge in detail in this article.

Summary

Energy problems and environmental pollution problems are increasingly prominent problems in today's society and are highly valued by the country. Therefore, it is imperative to find new energy vehicles that can reduce exhaust emissions and make better use of energy in the automotive electronics design industry. Electric vehicles are fully recognized and developed precisely because of the above characteristics.

It can be seen that the electric vehicle transmission system, as a very important link in the entire automotive system, also needs everyone's attention and research. It is a very necessary and arduous task to develop a better performance electric vehicle transmission system structure, provide power conversion and conversion capabilities, and improve the utilization rate of power. This article analyzes its working principle, transmission mode, advantages, and lists four commonly used topology architecture designs.