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Method of Controlling Common Rail Fuel Injection Device

The origin of high pressure common rail technology

12/4/2017 4:45 PM
As a child, diesel vehicles were mainly tractors, trucks and bulldozers used for farmland in rural areas. Later, with the understanding of automobiles, diesel engines were found Common Rail in many fields such as generators, ships, tanks, road construction machines, etc. heavy machine. But all in all, the diesel engine gives us the appearance of a 'big and powerful' big guy. So many people still holding the original eyes test the current diesel passenger car.

   Bosch first started mass production of passenger cars with a common rail fuel injection system in 1997, when Bosch and Mercedes jointly launched the Mercedes-Benz C-Class diesel with common-rail technology, while Alfa Romeo 156 was the first passenger to use the high-pressure common rail One of the cars. In the domestic car, Huatai modern common rail injection system. Diesel common rail system has been developed for 3 generations. The first generation of common rail high pressure pumps are always kept at their maximum pressure, resulting in wasted fuel and high fuel temperatures. The first generation common rail system was designed for commercial vehicles with a maximum injection pressure of 140 MPa and a passenger car injection pressure of 135 MPa. The second generation common rail system can change the output pressure according to the needs of the engine, with pre-injection and post-injection functions. With the control of the oil pump, jet pressure can reach 160MPa. Even in the case of low pressure, the system can also provide the right amount of injection pressure according to the actual situation. Not only helps to reduce fuel consumption, but also can reduce the fuel temperature, eliminating the need for fuel cooling device. Pre-injection reduces engine noise: A small amount of fuel is injected into the cylinder to ignite the fire and preheat the combustion chamber a few hundredths of a second before the main injection. Preheated cylinder pressure combustion after the main injection easier, the pressure and temperature in the cylinder is no longer a sudden increase, help to reduce combustion noise. Post-injection in the expansion process, resulting in secondary combustion, the cylinder temperature increased 200 ~ 250 ℃, reducing the exhaust of hydrocarbons. Bosch's second-generation common rail system products have been tested on Volvo S60, V70D5 and BMW's 230d passenger cars.

   The third generation common rail system with piezoelectric inline injector. In 2003, the third generation common rail system was introduced. The piezo actuator of the piezo common rail system replaced the solenoid valve, resulting in more accurate injection control. Eliminate the oil return pipe, the structure is simpler. Pressure from 20 ~ 200MPa elastic adjustment. The minimum injection volume can be controlled at 0.5mm3, reducing smoke and NOX emissions. The maximum injection pressure reaches 180MPa. This set of newly developed piezoelectric in-line injector system with pre-and post-injection rate curve more freedom. Common rail systems separate pressure generation from actual fuel injection compared to other injection systems. 'Rail' is used as a high-pressure accumulator, the internal fuel pressure is always maintained with the engine to adapt to the specific conditions of the best pressure. Common rail systems can be easily installed in a variety of different engines. In addition, the common rail system offers a broader range of expansion capabilities and greater degrees of freedom in combustion process design, enabling diesel engines Common Rail Injector to operate at lower emissions, with better fuel economy and low noise .

  Electronic control common rail system, is the domestic experts agreed that the highest level, the future will dominate an electronic control system. The special design of its injector can implement flexible multiple injection, and the injection pressure can be adjusted under different speed and load conditions, the benefits to the engine is a very good indicator. Due to these factors, electric common rail technology has generally been adopted for the new generation of passenger car diesel engines

 

   Although diesel passenger cars were already available in the 1930s, the development of early diesel vehicles stemmed from the unique fate of the Soviet T-34 tanks during World War II - as the T-34 tanks were diesel-powered, they did not catch fire easily , Become the leader on the battlefield. Now the Chinese market is like the early international markets. When consumers talk about diesel vehicles, they often make a lot of jokes that 'the biggest advantage of a diesel vehicle is that it will not catch fire.' However, with the development of diesel technology, diesel engines are finding more and more attractive features: high torque, high life expectancy, low fuel consumption and low emissions. Diesel engines are the most realistic and reliable solution to automotive energy problems. Now every new car in Europe will be equipped with a diesel engine models, and in China to achieve this move may be only FAW - Volkswagen. However, an indisputable reality lies ahead of us: With the energy crisis and the gradual increase of the greenhouse effect, people have more and more motivation. Although electronic fuel injection has been widely used, solutions based solely on gasoline vehicles are not enough to solve these problems problem. So in the hinterland of the automobile industry - Germany did not stop the study of diesel engines for a moment. Even in China, the current use of diesel engine only 10 remaining models, namely Jetta, Bora, Audi, Kaidi, JAC Refine 5 passenger cars, Futian surfing, Jiangling Landwind, Huatai Telaka, Shanghai Wanfeng, Liaoning dawn 5 SUVs. The 2.5-liter diesel powered by the Swiss-made diesel car is the introduction of the D4BH engine from South Korea's Hyundai Motor Company. The four diesel-powered passenger cars of FAW-Volkswagen all use Diesel engines from Volkswagen and Bosch, all of which are Plug pump, pump nozzle technology.

  Diesel has the advantage of: fuel-efficient, environmentally friendly, powerful, economical, easy maintenance, as long as the solution to the shortcomings have greater market prospects, and the realization of electronic control diesel program now appears to be a good solution. Diesel control to achieve three technical roadmap, respectively, single pump, pump nozzle and high pressure common rail. At present, major international auto parts suppliers are developing diesel common rail injection systems such as Bosch, Delphi, Siemens, Denso, VDO and Magna-Magneti Marelli, which are the world's leading suppliers of common rail injection systems However, only the Bosch family currently produces diesel injection systems in the domestic market. The following describes the three technologies:

1. Single pump technology
Delphi uses a single-pump system on heavy vehicles. Speaking from the cost, the domestic engine from Europe Ⅱ to Europe Ⅲ upgrade, if the use of single pump, the engine changes very small, only plug-in camshaft box instead of Euro Ⅱ inline pump can be. When the upgrade from Euro Ⅲ to Euro IV, the structure of the fuselage of the engine remains the same as long as the mechanical injector in the Euro Ⅲ system is changed to Delphi's electronically controlled injector to form a single-solenoid pump system with double solenoid valves. The overall structure of the engine does not make big adjustments, you can reach Euro Ⅳ emission levels. In the single pump is similar to the common rail I2C system consistency control, to optimize the performance of the entire system. In the fuel supply control, if using a dual solenoid valve single pump system, not only can control the pressure, you can also control the injection, but also can use multiple injection. It can reach Euro IV or Euro V standards. At present, Delphi's double-solenoid valve single-pump system is mass-produced in Europe and mainly supplied to Euro IV engines. Euro V standard engine-related systems are being developed. Another advantage of a single pump system is its reliability and longevity, which have been proven in millions of vehicles by 10 or even 15 years of actual use in Europe and North America. Monomer pump system in the engine during use, you can guarantee low emissions and fuel consumption. At present, this very enhanced, very reliable performance and service life is still further improved. Therefore, from the Delphi point of view, technically, it is believed that by 2010, the vast majority of heavy vehicle manufacturers in Europe and North America will adopt the single pump system and pump nozzle technology. Delphi is also developing a new system required by the new emission regulations after 2010.

2. Pump nozzle technology

Excellent mixture is to improve diesel engine power, fuel economy; reduce emission rates, the key factor of noise rate. This requires injection system to produce high enough injection pressure to ensure good atomization of fuel, but also must accurately control the starting point of injection and fuel injection. The pump nozzle system to meet the stringent requirements. As a result, as early as 1905, Rudolf Diesel, the founder of a diesel engine, proposed the concept of a pump injector, envisaging the combination of a pump and a nozzle, eliminating the need for high-pressure fuel lines and achieving high injection pressures. In the 1950s diesel engines with intermittently controlled pump injection systems were used on ships and trucks. Volkswagen and Robert Bosh AG then worked together to develop a solenoid-controlled pump injection system for passenger cars. CRDI stands for Common Rail Direct Injection in English. It refers to high pressure common rail diesel direct injection technology, CRDI technology and SDI (naturally aspirated direct injection diesel engine) technology, TDI (direct injection turbocharged diesel engine) technology Diesel engine technology developed by Bosch Germany. Common rail system consists of high pressure pump, fuel injection pipe, high pressure accumulator (common rail), fuel injector, electronic control unit and sensor and actuator. Common rail fuel injection system is the main contribution to the injection pressure Common Rail Shim and injection process completely separate from each other through the precise control of the oil pressure within the common rail so that the pressure of the high pressure tubing and the engine speed has nothing to do. This innovation in diesel engine technology minimizes vibration and noise in diesel engine models while further reducing fuel consumption and making emissions cleaner. However, common rail fuel injection pressure is lower than the pump system, generally only reached about 160MPa. Due to the wide range of injection pressure regulation, diesel vehicles adopting common rail technology can adapt to various working conditions better, and start with no difficulty.

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