The Research and Application of Lightweight Automobile Structure Are in Full Swing

Lightweight automobile structure is to reduce the weight of the entire structure and every component assemblies through various technical means in accordance with the requirements for society, economy, and environment, while ensuring the performance of the automobile. Lightweight structure includes lightweight bodies, chassis, power systems, interior and exterior trims and air conditioning as well as the integration of chassis power systems, new architectures for electric vehicles, and the development of proprietary systems for new energy vehicles. Weight reduction of car bodies is the most effective way to reduce weight. The use of load-bearing structure is beneficial to weight reduction. The weight reduction of the body reduces the load of the chassis, and the weight of the chassis can further be reduced. The power system can be miniaturized, and the volume and battery of the fuel tank can be reduced. The weight of the automobile engine is second only to the body. Therefore, the modularization of components and the structure optimization of key parts are very important, such as direct injection supercharging to make engines smaller, reducing crankshafts and number of fan plates and width of fan plates, and replacing metal transmission chains with plastic teeth shaped belts. For traditional passenger cars, the weight of the body-in-white accounts for about 1/3 of the weight of the whole vehicle, so the weight of the body is very important. The lightweight coefficient of AIWAYS U5 is 2.29, and the structure design of "upper steel and lower aluminum" is adopted. The battery and body of an electric vehicle account for 80% of the total vehicle's weight. Therefore, the weight reduction of the battery and body is more effective. The thickness of the single cell is reduced; the number of single cells is reduced, and the size is reduced. The fuel cell power system has been installed horizontally, showing a highly integrated development trend. In addition, in terms of lightweight parts, the optimization design of the body structure can adopt advanced technology after determining the main performance parameters to optimize the section size, thickness of the sheet metal, remove redundant materials, and make the body parts simplified, small, thin walled, hollow and composite.
 
The process of lightweight car is slightly tortuous, but moves forward.
The Ministry of Industry and Information Technology of China announced that in 2016, the average curb weight of domestic passenger vehicles including new energy vehicles and excluding export passenger vehicles was 1410 kg, and the average fuel consumption was 6.39 L/100 km; the average curb weight in 2017 was 1438 kg, and the average fuel consumption is 6.05 L/100 km; the average curb weight in 2018 was 1456 kg, and the average fuel consumption has reached 5.80 L/100 km; the average curb weight in 2019 was 1480 kg, and the average fuel consumption has reached 5.56 L/100 km. There is still some distance from the national plan of reaching 5.0 L/100 km in 2020. Since the 21st century, the global average curb weight of automobiles has increased with the increase in requirements of comfort and smart accessories. In 2009, the average curb weight of passenger cars in China was 1,227 kg, and in 2012 it rose to 1,295 kg, an average annual increase of approximately 1.8%. Later, there was a significant increase due to the hot sales of SUV vehicles in 2013. With the stringent energy-saving and emission reduction regulations and the R&D and adoption of new materials such as high-impact steel and plastics, structural optimization and process improvement, it is expected to decline again. By 2020, the global average curb weight of passenger cars will drop to about 1,600 kg. BAIC has announced that by 2020, the average curb weight of all newly developed models of BAIC Group will be reduced by more than 10%. Working both ways of subsidy policies and strict pollution control, the number of newly launched micro, small, compact cars and new energy vehicles in 2016 increased day by day. In 2016, the average curb weight of new energy passenger vehicles included in the purchase tax exemption was 1205 kg. The average total mass of the battery pack is 263 kg.
 
The market share of new energy vehicles dominated by pure electric vehicles is increasing. New energy vehicles are generally heavier than similar vehicles due to the energy storage of the battery. It is imperative to reduce the number and volume of batteries. In the past ten years, through selecting new ternary materials containing high nickel and increased development of solid-state lithium battery systems, there are certain breakthroughs in power battery's performance. The modularization of battery packs reduces the power battery's loading capacity, which solves the early problems of rebound caused by sacrificing weight reduction of pure electric vehicles for continued driving. The integration of motors, reducers, inverters is becoming more and more perfect. The chassis and power system of pure electric vehicles have realized integrated design. The third-generation electric drive system reduces weight by about 15% compared with the second-generation. With the breakthrough of silicon carbide technology, domestic motors and motor controllers, reducers, and inverters will be integrated. Electric vehicle models are gradually transformed from traditional models to new developments, and innovative aluminum alloy extrusions, stampings and castings have been applied. In addition, with the deepening of electronic and intelligent research, the traditional cumbersome transmission system for some models will be partially or completely electronic. For example, in March 2017, Volkswagen released a fully automatic driving concept car, and the steering wheel, accelerator pedal and brake pedal were eliminated in the car. It can be seen that in the past five years, the overall weight of domestic passenger cars has increased slightly due to the increase in electronic products and intelligent vehicle-mounted systems. However, fuel consumption has decreased and the quality has been improved due to the improvement of the performance of the engine and battery.