Chery Kunpeng Hybrid DHT has such a complex structure, is it good?

Let’s talk about Chery Kunpeng Hybrid DHT.

Its structure is 1.5T engine + dual motors, three-speed gearbox, and maximum torque is 510 Nm. This is a two-wheel drive, not a four-wheel drive dual motor model. BYD or Great Wall's ordinary hybrid two-wheel drive has only one drive motor, but Chery's can be driven by two motors. There are three pure electric drive modes alone, and two parallel drive modes, which can realize pure electric drive of single and dual motors, parallel, engine direct drive and other modes. In terms of mode, it is much more complicated than BYD and Great Wall.

Since the official information provided is relatively limited, we found a patent applied for by Chery Automobile. Based on this patent and the official drawings, we will talk about it in detail.

Figure: Chery's hybrid DHT patent diagram

Figure: BYD's super hybrid DMi patent diagram

Figure Note: Simplified diagram of Chery Kunpeng DHT hybrid driving mode

(Note: Compare with the simplified diagram of BYD DMi driving mode)

The patent description clearly states: the positions of the two motors, the positions of the "speed gears" of the three "gears", and the logic of the three sets of "clutch" controls:

1. Clutch C1 controls whether the engine is involved in the entire power system;

2. Clutch C2 controls whether the power passes through the 1st and 3rd gears.

3. "Clutch C3" mainly controls whether the power passes through the "speed gear" of the 2nd gear.

Comparing it with the structure of BYD DMi, you will find that the biggest difference is that both the engine and the motor must go through three sets of clutches and a three-speed gearbox to output power to drive the wheels.

First of all, in pure electric operation, it has three modes: electric drive mode driven by two motors P2 and P2.5 respectively, and electric drive mode driven by two motors at the same time. Ah, this is the thinking of a science and engineering man. I am not afraid of your complexity, but I am afraid that you are too simple.

"P2 motor pure electric drive mode": When cruising at low speeds with low power requirements, only the "P2 motor" ("motor 1" in the figure) is needed for driving. At this time, the "clutch C1" is decoupled and the "engine" does not participate in the work. In addition, the coupling control of "clutch C2" and "clutch C3" can be used to switch between 1st, 2nd and 3rd gears to meet the corresponding power requirements;

"P2.5 motor pure electric drive mode": When the power demand increases, the slightly more powerful "P2.5 motor" ("motor 2" in the figure) outputs power through the second "input shaft", and the 1st and 3rd gears can still be shifted at this time;

"Dual-motor pure electric drive mode": When the power demand increases further, the two "motors" work in parallel, and through the combination of two sets of "clutches", four combinations of 1st gear, 3rd gear, 1+2 gear and 2+3 gear can be achieved.

Parallel mode: There are 2 parallel drive modes

"Single motor parallel drive mode": "Clutch C1" is coupled, "P2 motor" and "engine" work together on the first "output shaft". At this time, "Clutch C2" and "Clutch C3" perform 1st, 2nd, 3rd gear shifting;

"Dual-motor parallel drive mode": When sudden acceleration, climbing a slope, changing lanes or overtaking are required, the power demand reaches the highest level. At this time, all components that can output power fully output power, and the speed ratio is adjusted through 3 "clutches", which can achieve power transmission combinations of 1st gear, 3rd gear, 1+2 gear and 2+3 gear, and fully exert the power performance.

Series mode: 2-speed adjustable drive

The logic of the series mode is the same as that of other DHTs. The "engine" drives one "motor" (P2 motor) to generate electricity, while the other "motor" (P2.5 motor) drives the car.

Engine direct drive mode: 3-speed adjustable drive

The engine direct drive mode is slightly different from other DHT logics. The logic under this condition is the same as that of traditional fuel vehicles, except that general fuel vehicles use a 6-speed or 7-speed "dual clutch transmission", while Chery's DHT only has 3 gears, which greatly reduces fuel economy. Therefore, the engine direct drive mode of the "Chery Kunpeng DHT hybrid system" is used as a fault backup mode, mainly for situations where the "electric drive system" fails, such as a serious battery loss or a "motor" failure that causes the system to fail to drive electrically. It should not be used often.

From the structure of the Chery Kunpeng DHT hybrid system, we can see some shadows of the traditional dual-clutch transmission. It also seems to be a structure between BYD's DMi-DMp.

Just from the number of components in the whole set of "DHT" (1 "engine", 2 "motors", 2 sets of "motor controllers" and 3 sets of "clutches", 3 sets of gear transmissions, etc.), the manufacturing cost is relatively high. You can understand that this once again reflects the characteristics of Chery's "engineering straight man" - not afraid of tediousness. This kind of story actually happened to GM's hybrid. GM felt that Toyota's single-row planetary gear was inefficient, so it made a double-row planetary gear. Honda and BYD directly replaced Toyota's single-row planetary gear with a clutch. This is the complete difference in the design ideas of technical engineers.

However, there are some issues with Chery's hybrid structure that are worth discussing.

1. The three pure electric driving modes driven by dual motors certainly make it easier to adapt to various working conditions such as low-speed starting, high-speed cruising, frequent start-stop, etc. However, the power of the two motors of Chery Hybrid is very small, one is 55kW and the other is 70kW. Even in the "dual motor pure electric driving mode", the theoretical maximum power is only 120kW, which is not as high as BYD's smallest motor of 132KW. Why doesn't Chery make two more powerful motors? This is a question worth thinking about.

2. How efficient and stable are the transmissions with multiple gears and multiple clutches (Chery calls it "dual-axis TSD" transmission)? As mentioned before, the direct drive with the engine is very inefficient and basically not used; the combination with two motors can theoretically adjust the speed of the dual motors, just like adding three gears to a pure electric car, which can make it easier to stabilize the speed and improve efficiency. However, when switching between oil and electricity, will there be more frustration? You can refer to the frustration of the dual-clutch transmission. The more parts there are, the more reliability and fault repair will be a problem.

3. 19.27kWh ternary lithium battery pack

The Chery Tiggo 8 PLUS Kunpeng e+ and Xingtu Zhuifeng ET-i versions both use a 19.27kWh battery pack, which is a bit small. Even Changan is equipped with a 30.7kWh battery pack. The Great Wall's 200KM range has a maximum of 39.76 degrees of battery pack. The 2022 BYD Tang ( parameters | inquiry ) that has just been declared and has not yet been launched has a battery capacity upgraded to 45.8kWh, and the two-wheel drive version has a WLTC range of 215km.

The supplier of Chery's plug-in hybrid battery is Guoxuan High-tech, which is also an Anhui company. The pure electric range is about 100km. Obviously, Chery's plug-in hybrid does not use a large battery to provide a longer pure electric range. And it is not clear whether this hybrid system supports fast charging technology.

Although the battery is small, its comprehensive range is more than 1,000 kilometers, which is acceptable. At the same time, because the battery is small, this is also one of the biggest reasons why Chery's plug-in hybrid has a good cost performance and is not priced too high.

4. The motor is small. Chery is famous for its engines, so the engine power should be larger, right?

This hybrid engine, codenamed SQRE4T15C, was actually first installed on Arrizo 5, and was originally codenamed SQRE4T15B. It is a National Five standard, and in 2018, the exhaust system cooling system was redesigned. Carbon emissions were reduced and reached the National Six standard, and the suffix code was upgraded from b to c, but it is still a traditional cast iron cylinder block with a heavy weight and no high-pressure direct injection system. It still uses standard manifold injection.

The maximum power is 156 horsepower and the peak torque is 230 Nm. In comparison, the Mocha DHT-PHEV engine is 156 horsepower and the peak torque is 235 NM. The BYD Tang DM-i 112 km range engine has 139 horsepower and a peak torque of 231 NM. The total power of Chery's dual motors is 170 horsepower, the motor power of Mocha DHT-PHEV (two-wheel drive) is 177 horsepower, and the motor power of Tang DM-i 112 km endurance version is 218 horsepower. Finally, the total power of Chery's plug-in hybrid is only 326 horsepower, and the total power of Mocha DHT-PHEV (two-wheel drive) is 333 horsepower; BYD Tang DM-i 112 km endurance version still has the largest power, which is 357 horsepower; finally, the 0-100 acceleration time of Chery Tiggo 8PLUS Kunpeng e+ is 7 seconds (body weight 1.74 tons), Mocha DHT-PHEV (two-wheel drive) is 7.4 seconds (body weight 2.13 tons), and BYD Tang DM-i 112 km endurance version is 8.1 seconds (body weight 2.13 tons).

If you think that the bodies of Mocha and BYD Tang are both more than 4.8 meters long and are not in the same league as Tiggo 8PLUS, you can take a look at Song PLUS DM-i and Macchiato DHT-PHEV.

In terms of performance, Chery's plug-in hybrid is just average. Of course, Chery officially claims that the 0-100 acceleration is less than 5 seconds. Perhaps other models can do it, such as the lighter Arrizo series.