Dual-motor dual transmission is still the mainstream
Not long ago, Nanjing Yuebo Power Systems Co., Ltd. signed long-term strategic cooperation agreements with Dongfeng Special Auto, Xiamen Jinlv, Zhongtong Bus, Changan Bus, Nanjing Jinlong and other enterprises. They plan to assemble 30,000 to 40,000 sets of dual-motor dual-transmissions. New energy vehicles. Prior to this, Nanjing Yuebo has supplied nearly 10,000 sets of powertrain products to pure electric commercial vehicles. What advantages do these companies have for the dual-motor dual transmission?
The motor can be started instantaneously and enter high-speed operation in a short time, which is almost unaffected by high temperature and cold weather. The motor drive is also considered to be the future development direction. However, the motor drive also has a short board. Li Zhanjiang, chairman of Nanjing Yuebo, said: "The efficient working area of the motor is relatively narrow. The combination of the motor and the transmission is the efficient working area of the motor through repeated changes in the gear ratio. The motor can achieve maximum efficiency and consume the least energy in the efficient working area. ”
The advantages of motor + transmission are widely recognized and accepted, and become the mainstream driving method. Li Zhanjiang said: "At present, many enterprises adopt the single-motor single-transmission method, which still has disadvantages such as low efficiency and high power consumption, which restricts the application and promotion of new energy electric vehicles."
The difference between the weight of the new energy vehicle and the full load is large, and the electric bus is more obvious, which makes the single-motor single transmission need to adapt to a wider range of working conditions. In order to meet the driving demand, large-sized motors are often used in new energy vehicles. The large motors are relatively large in size and the weight is also greatly increased. Li Zhanjiang said: "The most important thing is that in order to adapt to a wide range of working conditions, the motor is often not in an efficient working state and will inevitably consume more battery energy."
The dual-motor dual-transmission uses two sets of motors with different performances. One high-efficiency zone is at low speed, and one high-efficiency zone is at high speed. Each motor has two gears at the same time. With the load or vehicle speed change, the working states of the two motors are flexibly adjusted. Ensure that the motor works as efficiently as possible. Li Zhanjiang said: "The motor is always in an efficient area, which can save battery energy and increase driving range."
According to Li Zhanjiang, the current mainstream 10m commuter bus direct drive system on the market consumes about 1 kWh per kilometer. Nanjing Yuebo's dual-motor dual-transmission system does not exceed 0.8 kWh. In the case of the same battery capacity, the battery will be used. The driving capacity has increased by more than 20%.
The dual-motor dual-transmission system uses two motors, and the total weight of the motor has dropped by 40%. Li Zhanjiang said: "The dual-motor dual-transmission system can flexibly adjust the working state without the need for a large motor, and two small motors can meet the requirements."
"The dual-motor dual-transmission powertrain system has an advantage." Li Zhanjiang said, "At present, except for the CVT (continuously variable transmission), there will be power interruptions of several tens of milliseconds. The uneven power output will result in poor control performance. Especially for off-road SUVs, power interruption is a serious problem. The dual-motor dual transmission does not use CVT, but the two systems can flexibly adjust the working state, which can eliminate the phenomenon of power interruption."
The reporter visited the DET product of Nanjing Yuebo, with a maximum power of 240kW, which can achieve continuous changes of 0~4200N•m, ensuring uninterrupted power. The motor is integrated with the transmission and is not an imaginary behemoth.
The motor + transmission drive system also has a short board. Cai Wei said: "Brake energy recovery is one of the important technologies of new energy vehicles. The braking energy recovery effect of the motor + transmission drive system is not ideal."