The first China independent research and development and production of 7-speed dual clutch transmission came out

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In recent years, with the development of automotive technology, China's automobile industry has undergone tremendous changes. Many Chinese IT companies have invested in the automotive industry and established multiple electric vehicle brands. Chinese traditional automakers have also begun to take action. Many new brands have been launched, all of which show that the development of China's auto industry has entered a new phase. Chinese automakers are more focused on independent research and development, especially power systems. Many Chinese automakers are developing or starting mass production of self-developed DCTs and hybrid systems, accelerating local development and production as a new trend in China in the next few years.

Gai Shi Automobile reporter learned at the CTI China Forum held recently that the first 7D dual-clutch transmission 7DCT450 independently developed and produced by China has been successfully developed by Great Wall Motor. Zheng Lipeng, deputy dean of the Great Wall Automotive Transmission Research Institute and project director, gave a detailed introduction to the product from the development process, 7DCT450 technical characteristics, engineering capabilities and test conditions.

It is understood that since the launch of the 7DCT450 project in April 2014 and the successful mass production into the market in April 2017, it took only three short years. Zheng Lipeng said that in addition to achieving the best product quality, 7DCT450 has a compact design suitable for all platforms of the vehicle, meeting the needs of high output, and has excellent supplier system in parts, software, calibration and production equipment. Self-control ability. "The 7DCT450 is currently equipped with the corresponding four engine models. It is used in the Euro 5 operating conditions. In the future, we will also comply with Euro 6 emissions. The design is fully implemented from H2 models to VV7 and H7. cover."

7DCT450 vehicle loading situation

Positioning clear technology leadership

In terms of product positioning, why should the front-end predecessor Great Wall Motor develop DCT instead of AT? According to Zheng Lihua, DCT is easier to mount (precursor), has a wider tooth ratio span (>8), and can be equipped with centrifugal mode. Damper DMF effectively improves NVH, with better shift quality and dynamic characteristics, can expand to a larger speed ratio range, more gears and hybrids, can improve fuel economy by more than 20%, and at the same time mold cost Low, and can learn from the experience of manual transmission development and production.

Based on this, 7DCT450 is technically advanced in the design of the whole box, such as: with the lowest oil viscosity, compatible centrifugal pendulum vibration absorber DMF, lubrication flow controllable, support for matching electronic pump, with low leakage solenoid valve, unique The control strategy ensures that the optimal shift NVH, wet dual clutch and electro-hydraulic control module ensure high reliability and stability, superior cooling system, and electronic parking system. The specific technical parameters of 7DCT450 are shown in the figure below. .

7DCT450 technical parameters

The 7DCT450 has several outstanding technical highlights:

The first is to adopt a low-energy system design concept. The system-level energy reduction scheme is adopted to achieve item-by-item optimization; the transmission support scheme adopts the output shaft ball column configuration and the input shaft ball-ball configuration scheme to achieve better energy consumption efficiency; the low lubricant amount reduces the whole box. Run the oil loss.

The second is ultra low viscosity lubricants. With the lowest viscosity lubricant in the DCT transmission market: 4.1cSt@100°C, the low viscosity design ensures high transmission efficiency and is perfectly matched with the clutch friction material 6910 to ensure stable friction performance. It is excellent in compatibility with various materials at all temperatures (-40 to 140 ° C).

The third is to use a dual pump system. At the same time, the mechanical pump and the electronic pump are used, the electronic pump can be directly switched to the lubrication circuit, and the efficiency is high; the intelligent on-demand start-stop strategy is adopted, which is about 2%-3% energy-saving compared with the single-pump scheme, and is compatible with 48V and high-pressure hybrid.

The fourth is to use a highly reliable clutch + cooling system. The new friction material 6910 is used to effectively improve the glaze resistance of the friction material and the stability of the friction performance. The optimized friction plate groove design reduces the drag loss of the clutch and increases the heat dissipation capability of the friction plate. The high-efficiency intelligent cooling control system ensures that the friction material works in the optimal temperature zone during the whole life cycle, with less wear and tear, and has the vehicle full-terrain clutch thermal control drivability.

Fifth, it can be directly shifted. The shift control system is composed of a pressure regulating valve and a two-way flow solenoid valve, so the shift control logic is extremely flexible. The solenoid valve directly controls the shifting actuator and has the advantage of fast shift response at high and low temperatures. The eight fork pistons are controlled by four independent solenoid valves, which can be switched at will.

Sixth is the development of advanced NVH systems. The 7DCT450 NVH is designed with "more quiet design and more sturdy transmission". It uses the optimal DCT micro and macro design to carry out reasonable shafting layout, phase relationship and micro-shaping parameter design and Tip in/out and Shift noise optimization. Achieve diversity of powertrain 1D/3D co-simulation and NVH matching parameter optimization. DCT simulates key NVH performances such as vibration, noise, flow noise, vibration fatigue, and TPA at the vehicle level.

Seven is the advanced CAE simulation method. The multi-objective topology optimization method is used to reduce the weight of the part. The system's component analysis method is used to analyze the stiffness, strength and durability of the components. Advanced fluid simulation method, spatter lubrication, forced lubrication analysis of the whole box, strength and efficiency analysis of valve body and pump parts.

Eight is the development of transmission software. Innovative software control with self-learning based on the new downline transmission and different stages of use, protection and alarm strategy for the vulnerable parts of the transmission body, comfortable shifting strategy and fast and accurate physical model based clutch The oil-filling strategy meets the ASIL C rating for driving safety.

Nine is the transmission calibration development. The rig calibration of the hydraulic system and the electronic control system provides accurate basic data for vehicle calibration, improving vehicle performance and shortening the development cycle. In the extreme environment of high temperature and cold plateau, the vehicle performance of the transmission was fully verified, and the stability test of the transmission software in the mountain road and the bad road was implemented.

Strong and stable engineering capability support

The 7DCT450 is fully produced and tested by the Great Wall Auto Transmission Division. The Great Wall Auto Transmission Division is located in the Xushui Economic Development Zone in Hebei. The entire plant covers an area of ​​145,000 square meters. In March 2017, the first phase of the SOP was achieved with a capacity of 500,000. At the end of 2017, it is planned to realize the commissioning of the second phase of the 500,000 capacity production line, reaching 1 million capacity, and the second phase SOP will be realized in 2018.

In terms of product processing, Xushui Factory can complete shaft/gear machining, heat treatment, thermal post-processing, housing processing, transmission assembly assembly, fully automatic EOL test line, automatic refueling and function/performance testing, and NVH online inspection.

Zheng Lipeng, Associate Dean and Project Director of Great Wall Automotive Transmission Research Institute

Test technology development escorts quality

In the development of bench test technology, Great Wall Motor discovered softer earlier by adopting 20 transmission assembly gantry and 9 component rigs, as well as a complete test system covering parts, assemblies and complete vehicles. Hardware issues, faster and more comprehensive development of design changes with improved performance.

In the development of vehicle test technology, the complete transmission vehicle DVP system was adopted, and the vehicle test project reached 26 items. Great Wall Motor used more than 1,000 test vehicles for calibration and vehicle endurance test, matching 4 engines, involving all the transverse vehicle platform models of Great Wall Motor, the whole vehicle in the plateau, high temperature, low temperature, high humidity, mountain road, desert Extreme environmental testing ensures that the vehicle is stable and safe to ride in any environment.