Chinese passenger car electric drive market ushered in a diversified competitive landscape

In February 2017, the National Development and Reform Commission, together with relevant departments such as the Ministry of Science and Technology, the Ministry of Industry and Information Technology, and the Ministry of Finance, organized and published the “Guidance Catalogue for Key Emerging Industries Key Products and Services (2016 Edition)” (abbreviated as “Catalogue”). Among them, among the products that are newly cultivated by new energy vehicles, the centralized motors occupying the market's main positions, the wheel motors that have just entered the market, and the hub motors that are in the research and development stage are all on the list.

At present, the drive system of China's pure electric bus power system is mainly divided into two categories: centralized drive and decentralized drive. At present, the domestic passenger car market is mainly focused on centralized drives, and the two decentralized drive forms, wheel-side drive and hub drive, are gradually being introduced into the market.

â–  Centralized driving is the mainstream of the current market

The central drive system of pure electric bus can also be called centralized drive. The drive form is based on the drive system of the traditional power car. The main motor is connected to the drive axle through the drive shaft. In short, it is the power of the traditional internal combustion engine. The system was replaced with a motor-centric drive system.

“Centralized drive is divided into single motor and dual motor, single motor has direct drive, motor + change / reducer and central drive bridge in three forms. Dual motor program has dual motor parallel + change / reducer, double The motor series + change / reducer scheme and two motors + change / reducer (two motors are separated at both ends of the transmission) etc." Said Chen Youfei, deputy general manager of the Pure Electric Division of Suzhou Luhua Transmission Technology Co., Ltd. The method can meet the passenger car products of various specifications respectively, and belongs to the more mature type of technology.

“ Among them, the direct drive motor is the most widely used one in the current pure electric bus. The system is connected to the drive axle through a drive shaft through a drive shaft. The structure is simple, high reliability and easy to maintain.” Jingjin Electric Technology Co., Ltd. Relevant person in charge of the company said that due to the high maturity of the direct-drive motor technology, it is easier for customers to accept it, which is why bus companies generally adopt the direct-drive motor program.

In addition, the central drive axle can be seen as an upgraded version of the centralized drive. It is understood that the central drive axle is to place the motor horizontally on the drive axle. Since the final drive is eliminated, it helps to reduce energy consumption. At the same time, the integrated design also reduces overall weight. At present, it is on vehicles under 8 meters. Have certain advantages.

“However, although the centralized drive technology has a high level of maturity, there are also deficiencies in terms of subdivided drive solutions. For example, direct-drive motors have poor climbing performance, low-middle-speed performance, high weight, and high cost. Higher issues," Chen Youfei pointed out.

“Even so, car companies will initially choose a centralized drive technology program for the sake of products to be put on the market soon.” Wang Xiaoquan, director of the Southeast Automotive New Energy Technology Office, explained in an interview with a reporter from China Auto News that the new energy bus In the early stage of marketization, the policy dividend was the main driving force. The car companies would certainly seek a quicker change of drive solution to quickly seize the market, and centralized drive technology was the best solution at that time.

â–  Decentralized driver gradually becomes the future development trend

"With the deepening of the research of pure electric vehicle technology, the layout of its drive system has gradually evolved from the centralized drive of a single power source to the decentralized drive of multiple power sources." Head of Electric Drive System Design of Beiqi Foton Motor Co., Ltd. Wang Hailong pointed out that compared with the centralized drive, the decentralized drive eliminates transmissions, drive shafts, mechanical differentials, and half shafts, and moves the motor to the wheel side to make the drive structure simpler.

The most common type of decentralized driving is the wheel-side driving. The driving mode is to arrange the driving motor beside the wheel and directly drive the wheels through the deceleration mechanism.

According to Wang Yongtao, an engineer at Hager Technology Center, the wheel drive has a very prominent advantage. “Firstly, wheel drive can make the vehicle drive system and vehicle structure more compact and compact, and it is easy to achieve an increase in low floor and standing area and passenger capacity. At the same time, it can also reduce the vehicle's center of gravity and improve vehicle stability. In addition, the wheel drive system has a short power train chain and can optimize drive and brake force distribution through energy management and power system control strategies to reduce energy consumption and improve vehicle fuel economy. Compared with internal combustion engines and concentrated motor driven vehicles, The wheel drive technology can also greatly improve the vehicle's dynamic performance. It can easily implement ABS, TCS and ESP functions through motor control technology. In addition, the system can improve the steering performance of the vehicle and effectively reduce Turning to a radius, or even zero turning radius, greatly increases steering flexibility, he said.

Compared with the wheel drive technology, the wheel drive technology, which is regarded as the ultimate solution for pure electric buses, takes the essence of “distributed drive” to the extreme.

"The biggest feature of the wheel hub motor system is the integration of the power unit, transmission and braking device into the hub, which greatly simplifies the traditional system of the electric vehicle." Wang Hailong emphasized that the chassis of the hub motor assembly is much less than the traditional chassis. Parts will have greater advantages in cost. In addition, its transmission efficiency is higher than that of the centralized drive and the wheel drive.

“The preliminary calculations show that the wheel hub motor system is 13% to 16% more efficient than the centralized drive. Although the wheel drive system is in principle based on the arrangement of the motor on the axle, the motor system will have a speed reduction mechanism. About 10% efficiency loss, while the hub motor is directly driven wheels, to avoid the problem of loss of efficiency." Tian Chao, chairman of the synchronization group, said Lu Chao.

Although the advantages are obvious, the technical problems with distributed drive technology cannot be ignored either. Wang Hailong pointed out that the unsprung mass change of the wheel-side motor will affect the ride comfort and handling of the vehicle; in addition, there is still no ideal solution to solve the wheel-drive differential problem, especially in the case of high-speed turning and bumpy roads. Differential control. The problem of in-wheel motor reliability and unsprung mass increase is even more pronounced. At the same time, as all components are concentrated in the hub, heat dissipation and electronic control issues are also urgently needed.

The high cost of a distributed drive solution is another important reason for its marketization. "Distributed drives require at least two motors and the cost is approximately three times more than that of direct-drive systems." Zhao Fucheng, vice president of Geely Automotive Powertrain Research Institute pointed out that the benefits and systems created by distributed drives in reducing power consumption The cost is not equal.

â–  Future market may be diversified

The industry generally believes that the new energy vehicle power system is divided into three stages of technological development. The first stage is the centralized drive technology, the second stage is the wheel motor technology, and the third stage is the hub motor technology known as the ultimate solution.

Judging from the current market structure, it is an indisputable fact that centralized drive technology occupies the dominant position in the pure electric bus market. So, decentralized drive technology as a more advanced drive program, the future can come from behind?

“Regardless of the scale of production or the economic benefits, centralized drive technology will be the mainstream of the pure electric passenger car market for a long time to come. This time will last for at least 3 to 5 years,” the industry source said.

In response, Wang Xiaoquan also pointed out that the dominant position of the centralized drive technology in the pure electric passenger car market cannot be shaken in the near future, and after 2020, the subsidy decline will make the marketization of distributed drive technology more difficult again.

Lu Chao is a supporter of the "subversion theory" of decentralized drive technology. He believes that wheel drive technology will occupy a place in the pure electric bus and pure electric special vehicle market. In addition, the market opportunities brought by the combination of in-wheel motor technology and automated driving will be even greater.

"The BYD K9 with wheel-side drive technology can be said to be a pioneer in the company's new energy bus segment." Xiao Haiping, director of public relations for BYD's commercial vehicle sales division, is very optimistic about the development prospects of wheel drive technology. In 2014, BYD carried wheel-side motors. After the introduction of buses in China, thousands of vehicles have been promoted in Nanjing, Hangzhou and Shenzhen. “While the mileage of this product in Shenzhen has exceeded 400,000 kilometers, the quality has been unanimously approved by users.”

It is understood that Futian Ouhui has mass-produced 18-meter wheel-driven pure electric products in 2015, and Hager has 12-meter wheel-side buses to export overseas. "I believe that in the future, decentralized drive technology will be the mainstream of the industry, and the cost will decrease as production increases," said Jiang Tao, chief engineer of Shanghai Futian Electric Technology Co., Ltd.

“It is undeniable that the wheel drive and wheel drive are the development direction of the new energy bus electric drive system.” Wang Hailong believes that the development trend of system integration and digital control will also help the rapid spread of distributed drive technology. “However, In terms of technology, distributed drive technology also needs to complete the accumulation of technology as soon as possible, and it will be possible to realize the accumulated market opportunities.