At present, three major companies in the world are developing and producing diesel high-pressure common rail systems, such as Denso Japan, Bosch Germany and Ford USA. * * * The rail system separates fuel pressure generation from fuel injection. If the single-pump diesel injection technology is compared to the revolution of diesel technology, then the * * rail can be called rebellion because it deviates from the traditional diesel system and is similar to the sequential gasoline injection system. * * * The railway system has opened up a new way to reduce diesel engine emissions and noise.
Because of its strong technical potential, today's manufacturers have turned their attention to the third generation of * * * rail system-piezoelectric * * * rail system. Piezoelectric actuators have replaced solenoid valves, thus obtaining more accurate injection control. Without oil return pipe, the structure is simpler. The pressure can be adjusted elastically between 200 and 2000 Pa. The minimum injection quantity can be controlled at 0.5mm3, which reduces smoke and NOX emission.
The increasingly serious energy crisis has become the focus of the world's internal combustion engine industry, and diesel engines are increasingly favored by users. Compared with gasoline engine, diesel engine has many advantages: it can reduce CO2 emission by 20%~25%, and has more advantages in acceleration performance at low speed, with an average fuel consumption of 25%~30%, which can provide more driving pleasure. Therefore, some people boldly predicted the development trend of diesel engine in global automobile production, and divided the proportion of diesel engine in world automobile production by region. However, compared with gasoline engines, the emission control of diesel engines is a difficult point. In order to meet the emission standards, the advanced fuel injection system of diesel engine-high pressure common rail technology has become the focus of attention in the industry. A few years ago, high-voltage rail technology was dominated by foreign capital, but now this situation has been broken.
The improvement of emission standards will inevitably promote the development of engine technology.
On June 30th, 2005, Beijing took the lead in implementing the national III emission standard. On July 3rd, 2006, KLOC-0, new cars in Shanghai's public transport and taxi industries implemented national III emission standards. On September 2006 1, Guangzhou began to implement the national III emission standard. In July this year 1, the third national emission standard will be fully implemented. By 20 10, the national four emission standards will be implemented.
The improvement of emission standards will inevitably promote the development of engine technology. For gasoline engines, it is not difficult to meet the current emission standards because of the relatively mature technology and aftertreatment. For diesel engines, most of them are mechanical fuel systems at present, and the development time of diesel direct injection technology is short, so the engine must be redesigned to meet the requirements of emission standards. At present, most of China adopts imported technologies to meet the current emission standards (National III), but some enterprises are conducting independent research and development, such as China FAW Wuxi Oil Pump Nozzle Research Institute and Chengdu Weite. Under stricter emission standards, in addition to the electronically controlled fuel system, many new technologies have been introduced into the whole engine. Ricardo, a world-famous automobile research and development organization, recommended the technical requirements of the engine at each emission stage. It can be seen that the * * * rail system is one of the most inherited and sustainable fuel injection systems because of its unique advantages.
High-voltage track system has been widely used abroad.
After the diesel engine fuel injection system developed from mechanical control to electronic control, the electronic injection system has undergone three changes, namely, position fuel injection system, timing fuel injection system and timing pressure fuel injection system (* * * rail system). The invention realizes the separation of pressure establishment and injection process, which makes the control process more flexible, can accurately control the small oil quantity and better realize multiple injections.
Since 199 1, Denso Japan published the paper on ECD-U2 high-voltage rail system, foreign fuel system manufacturers have invested huge amounts of money and manpower to develop the rail system. Bosch announced the high-pressure common rail system for cars in 1995. The system adopts radial plunger-rotor oil supply pump, and the solenoid valve of injector adopts ball valve structure. At present, Bosch's * * rail system has been widely used in European passenger cars and light vehicle diesel engines, such as German Daimler-mercedes benz c series cars, Italian Alfaremo156 cars, German Volkswagen's Audi V8 turbocharged diesel engine with 3.3L, Duramax6600 diesel engine jointly produced by American General Motors and Japanese ISBe3.9L, and American Cummins' 5.9L fully-controlled diesel engine. Delphi and Siemens introduced Multec DCR 1400 * * common rail system in 1998 and 2000 respectively, which adopted radial plunger-rotor oil pump and designed Delphi's injector solenoid valve in the injector, making the injector smaller. Siemens injector adopts piezoelectric actuator, which has shorter response time; The first generation product of ECD-U2 was developed by Denso Corporation of Japan at 199 1, and matched with J08C diesel engine of Hino and 6HK 1 diesel engine of Isuzu at 1995. After years of improvement and perfection, the latest products have been used in the ECD-U2P system of automobiles.
At present, * * rail fuel injection system is widely used. Bosch has produced 25 million sets of * * * rail systems, and invested in the construction of technical centers and factories in Wuxi, Jiangsu, realizing localized production. Great Wall Motor and Bosch Company have developed * * rail high-pressure diesel engines, and other brands such as Audi, Mercedes-Benz and Huatai have also introduced * * rail system vehicles. Some domestic universities, research institutes and enterprises have also achieved distinctive research results through cooperation or independent research and development, and dozens of patents have been published. Therefore, China has accumulated some experience in electronically controlled direct injection diesel engine, but there is still a gap with foreign countries in general, mainly reflected in the manufacturing process and quality control of mass production. In addition, the domestic supporting system of * * * rail system is not perfect, and some parts are imported, such as single chip microcomputer chip and * * * rail pressure sensor.
Competition between foreign companies and China enterprises is no longer dominant.
Compared with gasoline engines, electronically controlled diesel engines have a relatively small gap at home and abroad. This is because of two reasons: First, most original diesel vehicles in China have their own brands; Second, domestic diesel vehicles have low comfort requirements and low prices, and foreign companies do not have an advantage in competition with Chinese enterprises.
With the improvement of emission standards, diesel engines must adopt electronically controlled injection system. At present, the domestic diesel engine electronic control system mainly includes * * * rail and unit pump. Compared with foreign advanced technology, although it does not have the same strength, it has a good development momentum. For example, the * * rail system developed by Wuxi Oil Pump and Nozzle Research Institute has been used in Wuxi public transport, and a large number of domestic enterprises are engaged in the research and development of electronically controlled diesel engines, so the domestic electronically controlled diesel engine market will certainly make a difference in the future. The price of products provided by foreign companies is relatively high, and the supply price depends on the batch number. At present, it is difficult for them to get a satisfactory price under the premise that the batch of electronically controlled diesel engines in China is not large.
At the same time, the domestic independent brand system also has obvious advantages in after-sales service and spare parts supply. The competitiveness of domestic self-developed electronically controlled fuel system is mainly reflected in the following aspects: First, the price is cheap and the economic batch is small. Secondly, for light truck products, in the case of small batch, we can choose PM type in-line pump with high injection pressure+electronic governor+cooling EGR scheme, which is also our advantage. In addition, for medium and heavy vehicles, technical routes such as * * * rail and single pump have been implemented in the third stage in China.
Of course, there are still many challenges in the domestic electronically controlled diesel engine system, such as immature manufacturing technology and small batch; Fuel quality is difficult to guarantee; The level of diesel engine aftertreatment technology is not high. But these will be solved gradually over time.