SAIC shows off its trump card: detailed explanation of DMH hybrid system

Recently, SAIC introduced the latest generation of hybrid system, "SAIC DMH hybrid system", and the first model is Roewe's new sedan Roewe D7. The hybrid system is mainly composed of four parts, namely hybrid engine, super hybrid high-efficiency long-range battery, five-in-one PICU and dual-motor hybrid gearbox.

Let’s talk about what are the highlights of this hybrid technology.

Hybrid transmission: P13 architecture, P1 motor coaxial arrangement

First, let's look at the core DMH hybrid transmission. Its basic configuration adopts the most popular "P13 architecture", namely P1+P3 dual motors + first-speed direct drive. Compared with those 2-speed DHT, 3-speed DHT or even 4-speed DHT, its structure is simpler and more compact.

In terms of specific structure, it includes a P3 motor for driving, a P1 motor for generating electricity and adjusting the engine speed, a controller (5-in-1 PIUC) and a set of electromechanical coupling mechanisms.

It can be seen that SAIC DMH belongs to the most mainstream single-speed series-parallel hybrid system at present, but in terms of structural design, SAIC has its own ideas and creativity.

1. P1 motor coaxial arrangement

Slightly different from BYD DM-i's "EHS" structure, its P1 motor is coaxially arranged with the hybrid-dedicated engine. Compared with the parallel shaft arrangement, it has one less set of gears. The advantage of this is higher transmission efficiency and smoother operation. At the same time, SAIC said that such a design can also bring better NVH performance.

2. P1 motor and clutch are highly integrated

The C1 clutch is nested inside the P1 motor, making the overall structure more compact and the end winding shorter. According to SAIC, the axial length of the assembly is more than 10% shorter and the overall weight is more than 10% lighter than that of a general Hairpin winding motor, which can bring better

3. Cooling efficiency increased by 30%

The heat dissipation efficiency of the motor will also directly affect the motor's output power. In this regard, SAIC DMH's P3 motor uses direct injection oil cooling technology, which can shorten the transmission path and dissipate heat more directly. Compared with the traditional motor cooling system, the continuous performance is improved by more than 20%. The P1 motor adopts a winding immersed oil cooling design, which improves the cooling efficiency by 30%, so that the motor's continuous power can reach more than 80% of the peak power.

Overall, compared with the general single-speed DHT, SAIC's DHT is smaller in size and lighter in weight, but has higher output power and integration.

According to data released by SAIC, the maximum power of its motor is 150kW, the peak torque is 330N·m, and the mass power density is 6.1kW/kg. In addition, its P3 motor adopts a high-efficiency HAIR-PIN flat wire design, which has high power density and better heat dissipation performance. The official data is that the maximum efficiency is 97.5%, and the motor has a wide high-efficiency range, and the WLTC comprehensive efficiency is as high as over 90%.

4. Further optimize NVH

Finally, in terms of NVH, SAIC engineers adopted the classic double-V and six-stage skew pole design for the P3 motor rotor, which can achieve low motor torque pulsation and small rotor torsional vibration. At the same time, it combines the electronic control active harmonic injection technology to further improve the motor NVH performance.

Hybrid-specific engine: thermal efficiency up to 43%

In addition to the DHT gearbox, the other key part of the hybrid system is naturally the engine, which will directly affect the fuel consumption performance. This DMH super hybrid is equipped with a 1.5L naturally aspirated hybrid engine with a maximum power of 82kW, and its power parameters are at the mainstream level of the same level.

So what are the technical features of this 1.5L hybrid engine?

First, in terms of combustion efficiency, the engine's turbulent kinetic energy and combustion rate are effectively improved through the combination of high tumble ratio air ducts and compact combustion chamber design. For example, through high tumble air duct technology, the tumble ratio is increased by 64%; through combustion system matching optimization (compression ratio reaches 16:1), turbulent kinetic energy is increased by 23%. The benefit of this is that combustion efficiency can be improved.

According to data released by SAIC, its thermal efficiency is as high as 43%. In comparison, the thermal efficiency of the Leishen 1.5T hybrid engine in Geely's new generation Leishen hybrid system 8848 is 44.26%, and the thermal efficiency of BYD Xiaoyun's plug-in hybrid 1.5L engine is 43.04%.

Secondly, in terms of thermal management, the engine uses technologies such as electronic water pump, dual thermostats, and cylinder head double-layer water jacket to ensure that the engine operates in the optimal temperature range under various operating conditions.

In addition, this engine uses a mechanical and electronic dual oil pump integration, which can achieve precise control of cooling and oil output at all times, autonomous adjustment to save fuel and better performance. For example, at low speeds, the electronic oil pump intelligently supplies oil, which has better acceleration performance; at high speeds, the electronic oil pump is intelligently shut down, and only the mechanical oil pump is used to supply oil, saving more than 40% of the energy consumption of the gearbox hydraulic system.

Finally, reducing system friction is also an indispensable part of improving engine efficiency. This engine uses 18 friction reduction technologies in the piston, cylinder bore, crankshaft system, valve mechanism, chain system, lubrication system and accessory system, ultimately achieving a thermal efficiency of 43%.

Five-in-one PICU controller: Faster operation

In terms of control, this hybrid system uses a five-in-one PICU controller. It integrates five major managements, namely engine management, hybrid mode management, transmission management, battery thermal management, and air conditioning management. The advantage of integration is unified management and quick decision-making, that is, the decision-making mode of the past where five brains discussed with each other has become one brain managing five things.

Officials said that through a higher integration design, 70% of redundant components can be saved and the structure is more compact. Judging from the components displayed on site, the volume is indeed much smaller than that of previous generations of products.

Of course, in addition to reducing the physical size, it can also greatly reduce the network load and data latency in the car, which brings the benefit of improving the computing speed by 50% compared with before. Specifically for car models, the most direct benefit is the improvement of power response speed. For example, the power response time of Roewe D7 DMH is only 0.26 seconds.

Battery: No fire after puncture

In terms of batteries, SAIC DMH's battery module has realized a special battery pack that is detachable and repairable. A high-strength frame is designed on the outside of the battery pack, which can achieve puncture without fire and extrusion deformation of up to 30%, thus improving the thermal runaway blocking system.

Working mode: five-mode hybrid

In terms of working mode, the DMH hybrid will provide five driving modes, namely pure electric mode, series mode, full load mode, direct drive mode and energy recovery mode.

In pure electric mode, the power battery is directly connected to the P3 motor for driving; in series mode, the engine will drive the P3 motor to drive the vehicle and drive the P1 motor to charge the battery; in full load mode, the power battery and the engine will supply energy to the P1 and P3 motors at the same time; in direct drive mode, the engine will directly supply energy for vehicle driving. As for the energy recovery mode, I won’t say more here.

First model: Roewe D7 DMH

SAIC DMH's first model is Roewe's new sedan, the Roewe D7. Below we briefly sort out the information currently released about this car.

The Roewe D7 DMH is equipped with a battery with a capacity of 21.4kW·h. The official pure electric range is 125km, and the maximum oil-electric range is 1400km.

As we mentioned earlier, the feature of this battery is that the battery modules can be repaired individually. At the same time, the modular design allows the power to be adjusted between 9.5-24.5kWh, and the pure electric range can be adjusted between 50-150km to meet the needs of consumers with different needs.

In addition to the hybrid version, the Roewe D7 will also launch a pure electric version. The pure electric version was born on the SAIC Xingyun pure electric exclusive platform. It will provide two new magic cube batteries, with a corresponding CLTC comprehensive range of 510km and 610km respectively. In terms of power, the new car will have a VGA six-in-one motor, a permanent magnet synchronous motor with a maximum power of 155kW.

In terms of appearance, the front face of the new car adopts a new brand electric design language, which is different from the design of the existing Roewe series products and is more recognizable as a whole. Specifically, the new car still uses the closed front face shape commonly used in pure electric vehicles, which looks more concise. In addition, the car adopts a slender light group shape, which has a sharper visual effect. The lower surround adopts a black air intake design to enhance the sense of sportiness.

From the side, this car is equipped with hidden door handles and 18-inch low-drag wheels, which makes it look more technological. The rear is round and wide, full and full of tension. The taillights are slender, and the slightly upturned ducktail design on the edge of the trunk gives it a sporty feel.