Hybrid Technology Industry Analysis Report (2021) (Medium)

In October 2020, the "Energy-Saving and New Energy Vehicle Technology Roadmap (Version 2.0)" was officially released, clearly stating that by 2035, the annual sales of energy-saving vehicles and new energy vehicles in my country will each account for 50%, and all traditional energy-powered passenger cars will be converted to hybrid power. This means that the hybrid technology route, which has not received clear policy support before, has finally ushered in the spring of development. Looking at the domestic automobile industry, hybrid technology is flourishing, and foreign companies represented by Toyota and Honda and domestic brand companies represented by Great Wall and BYD are increasingly competing in hybrid technology. In order to let the industry better understand the development status of hybrid technology, the Automotive Evaluation Institute, together with industry experts, launched the "Hybrid Technology Industry Analysis Report (2021)" for reference by the industry.

Continued from the previous article: Hybrid Technology Industry Analysis Report (2021) (Part 1)

3. Technical analysis of hybrid power industry

3.1 Hybrid configuration represented by Toyota THS and Honda i-MMD

3.1.1 Toyota THS hybrid system

Toyota's THS hybrid system couples the engine, generator and motor together through a planetary gear. The generator is connected to the sun gear, the engine is connected to the planetary carrier, and the motor is connected to the outer ring gear and connected to the wheel end through the main reducer.

Toyota THS hybrid system

Essentially, THS has only two working modes: pure electric mode and hybrid mode. In pure electric mode, the engine and generator do not work, and the motor drives the wheel end alone. At this time, the engine does not rotate, but the generator will reverse; in hybrid mode, the engine, generator, and motor work at the same time, the engine outputs torque, and the generator controls the engine speed. Together, the three ensure the stable operation of the planetary gear system. Braking recovery is only a function, not a working mode in the strict sense.

The advantage of Toyota's THS hybrid system is that due to the decoupling of engine speed and wheels, low vehicle speed can increase engine speed and have better fuel economy and power. But the disadvantages are also obvious: since the engine torque will always be distributed to the generator (sun gear) and wheel end (outer gear ring) in a fixed ratio, the engine torque is coupled with the wheel end, and reactive power circulation will occur under high-speed conditions, resulting in low efficiency, low-efficiency discharge of the generator, and low-efficiency charging of the motor. Therefore, the high-speed power performance is average, and good fuel saving performance cannot be reflected under high-speed conditions.

Toyota's THS hybrid system tends to be engine-driven, with the electric motor playing a more auxiliary role.

3.1.2 Honda i-MMD Hybrid System

Honda's i-MMD hybrid system is mainly composed of a 2.0L Atkinson cycle engine, E-CVT, generator, and drive motor. It is worth noting that E-CVT refers to the structure that connects the generator, motor, and engine through a gear shaft structure, not a gearbox.

Honda i-MMD hybrid system

Honda's i-MMD hybrid system can be divided into three working states: pure electric mode, series mode and engine direct drive mode. In pure electric mode, the vehicle is driven entirely by the electric motor, and the energy comes directly from the on-board lithium battery pack. If the power is insufficient, the gasoline engine will drive the generator to generate electricity, which is suitable for urban traffic jams and low-speed driving.

The series mode is a highlight of the i-MMD system. In this state, the engine is running but the clutch is disconnected. The engine drives the generator, and the generator (or combined battery) supplies power to the electric motor to drive the wheels. This mode is more efficient and relatively more fuel-efficient.

In the engine direct drive mode, that is, the engine is combined with the clutch, the engine can supply power to the generator while the torque can be transmitted to the wheel end through the clutch, driving the vehicle together with the electric motor. Compared with the series mode, the function of transmitting the engine torque to the wheel end is added.

Although the i-MMD system has only three driving modes, it is very efficient. In fact, during driving, the engine is not in the economic speed range in most cases. In the hybrid mode of i-MMD, because the engine does not participate in direct drive, the engine can be calibrated to the economic speed range to drive the electric motor to charge the power battery, and the battery outputs current to the drive motor to drive the vehicle.

The overall design concept of the i-MMD hybrid system is closer to the electric drive mode, so it is closer to an upgraded extended-range hybrid system.

3.2 China's rising star - WEY intelligent hybrid DHT and two Toyota technology comparison analysis

WEY intelligent hybrid DHT system is the first series-parallel hybrid power system to be mass-produced in my country, with 100% independent intellectual property rights. The intelligent hybrid DHT system is also a hybrid power system with reasonable design, outstanding energy-saving effect and dynamic performance after Toyota THS and Honda i-MMD. This system includes three powertrains, covering 1.5L+DHT100, 1.5T+DHT130, 1.5T+DHT130+P4, and also provides HEV and PHEV solutions. The HEV architecture of the intelligent hybrid DHT is the first dual-motor HEV architecture of a Chinese brand, and it has a wide range of applications that can be explored.

WEY Intelligent Hybrid DHT System

The design concept of WEY's intelligent hybrid DHT hybrid system is also close to the electric drive mode. From the overall layout, it has the same purpose as Honda's i-MMD hybrid system. The structure of the intelligent hybrid DHT system is not complicated: the engine and two electric motors are connected through a parallel shaft 2-speed reduction mechanism, and the clutch is used to adjust the power output relationship between different components. Like the i-MMD hybrid system, the intelligent hybrid DHT can also achieve three modes: pure electric, series, and engine direct drive. However, the difference is that the intelligent hybrid DHT uses a two-speed transmission mechanism. The purpose of adding a gear is to have an outstanding experience under different working conditions.

The most obvious difference between WEY's intelligent hybrid DHT and the hybrid systems of the two Toyotas is in high-speed operation. Since Toyota's THS hybrid system can only use hybrid mode at high speeds, its efficiency and experience are slightly inferior, so only the differences between the intelligent hybrid DHT and i-MMD hybrid systems are analyzed.

Under high-speed conditions, both the intelligent hybrid DHT and i-MMD hybrid systems use the engine direct drive mode, and the intelligent hybrid DHT uses a two-speed transmission. The biggest advantage is that in order to adapt to different throttle openings and driving strategies, it can have more dynamic or more energy-efficient performance.