Traditional mechanical engine fuel injection system, with its reliability and easy maintenance has been in constant development and use. Since the beginning of the 21st century, as people in the energy, environmental awareness and increasing demand, the pulse of the traditional engine fuel injection system has not be able to meet the demands of modern engines. Therefore, the engine of modern common rail fuel injection technology to avoid the shortcomings of traditional engine on the basis of the development has been rapid, fuel injection has become the main trend.
First, the traditional mechanical fuel injection system

Traditional mechanical fuel injection system as shown in Figure 1. These mainly include: fuel tanks, low-voltage, oil pump, fuel filter, high pressure fuel pump, fuel injector and tubing, and so on. The process is: the engine crankshaft gear driven fuel pump through the camshaft rotation, the fuel from the fuel tank to the pump, a low pressure, another fuel filter, part of the supply of high pressure fuel pump, to return to another part of the fuel tank. Access to the fuel injection pump, through high-pressure pipeline to transport fuel injector, when the pressure over the opening pressure injector, the injector opening, a fuel injection.
Diesel fuel pump depends on the control of the engine. Mainly reflected in: Engine provided the impetus to the fuel pump, engine rotation every 2 laps of the Work 1 cylinder, fuel pump rotating a circle, each cylinder fuel injection to 1. This view, the overall fuel pump fuel injection engines from time to indirect control, and engine oil pressure with larger changes in engine speed. Injection is the advance in the engine to higher fuel pump when the corresponding advance of the camshaft angle, to meet the requirements of the engine at high speed. Governor through the induction of various engine components perception condition, the diesel engine control, mainly to meet the stability and idling over the demarcation of speed off oil, the remaining conditions to rely on components and sensors within the governor The spring balance to stabilize the engine speed. Such a mechanical fuel pump in the form of main-line fuel pump and distribution of VE-pump.

The traditional mechanical diesel injection engine can not be a better moment to the fuel injection and fuel injection process control, has been unable to meet the requirements of energy-saving and environmental protection. Under these conditions, the electronically controlled common-rail diesel injection system came into being, and has been a rapid development.


Second, electronically controlled common-rail fuel injection system

1940s electronically controlled common-rail fuel injection technology in the aviation engine on the first application of the 1950s in the car engine on the wider application. In the 1990s, the diesel fuel supply electric control system began in the practical application of large-scale use. Major Japanese Denso Corporation and Toyota Motor Corporation ECD-U2 system, Bosch and DC-controlled companies, Common Rail fuel injection system.

(A) the composition of common rail systems

Compared with traditional mechanical fuel injection system, electronically controlled common-rail fuel injection system-much more complex, from the pressure to produce bodies of the fuel injection control agencies have a lot of improvement. Electronic Common Rail fuel injection system and the structure of the system in Figure 2 and plans were shown in Figure 3. These mainly include: high pressure for pumps, fuel filters, the high-pressure common-rail, electronically controlled fuel injection, electronic control unit ECU, all kinds of sensors. The agency decided to improve the common rail electronic control systems to the traditional mechanical fuel injection system has many advantages.
(B) the principle of common rail technology

Common Rail technology through the common rail direct. Or indirectly to a constant high-pressure fuel distribution to each injector and the help of integration in each injector on the high-speed electromagnetic switch the valve to open and close, timing, Quantitative control of fuel injector to spray the fuel combustion chamber, thus ensuring the best atomized diesel engine, combustion and the least polluting emissions.

Technology is high-pressure common rail pumps, pressure sensors and closed-loop system consisting of ECU, will spray and spray pressure of a process completely separate from each other's way of a fuel supply. From the high-pressure pump high-pressure fuel pipeline for conveying to the public through the public for the oil pipeline to achieve precise control, high-pressure tubing pressure size has nothing to do with the engine speed, engine oil can greatly reduce the pressure on the engine speed changes , So you will reduce the shortcomings of the traditional diesel engine. ECU fuel injection control of the injector and fuel injection depending on the size of the fuel rail (public for the pipeline) pressure and electromagnetic valve opened the length of time.

(C) common rail technology development stage

Diesel Engine Electronic Control abroad in the high-pressure common-rail fuel injection system of research carried out in the earlier and more in-depth, there are several common-rail system has been put into production, and a vehicle matching applications. Japan's Denso Corporation of ECD-U2 system is electronically controlled high-pressure common-rail fuel injection system of a typical representative of the system not only to achieve △ jet, but also to achieve pre-jet spray and Xue Xing.

The development of common rail injection generally has experienced three stages, as shown in table 1.
From Table 1 can be seen in: common-rail injection at the maximum injection pressure continuously improve, so improving the quality of the jet is of important significance. The higher the pressure, the better the atomization of fuel, the smaller the particles more evenly, burning more fully, economy, power and emissions of all good, but the injection system requirements are also higher; increasing the number of jet can be achieved Engine combustion and emissions to meet the many jet, can be controlled at different stages of combustion of fuel injection and injection rate, burning more fully, the thermal efficiency improved to a minimum of stability on the jet, each of the three stages of the decline in the volume of spray This shows when each jet can spray more uniform, more detailed, more fuel injection and just off oil, responsive, response characteristics, and this is conducive to combustion, reducing coke production.



(D) of the characteristics common rail technology

Common Rail Diesel technology is integrated computer-controlled technology, modern sensor detection technology and advanced fuel injection in a structure of the new technology. The main features of the technology are: ① use of advanced electronic control devices and switches with high-speed electromagnetic valve; ② using common-rail fuel supply means; ③ high-speed high-frequency electromagnetic-off valves, control flexibility; ④ facilitate the transplant system structure, the scope of adaptation - Canton.

The technology in use on the car, is the world automobile industry to meet increasingly stringent emission standards and to take the necessary steps.



Third, mechanical diesel injection and electronically controlled common-rail diesel injection compare the differences

Machinery and electronic control of diesel injection common rail diesel injection of the main differences in the performance of the supply of fuel to the fuel injection method and the moment of choice.

Traditional mechanical fuel injection system of hydraulic high-pressure pipeline is an instant high-voltage fluctuation, mainly by the plunger for the formation of oil. This pulse of the fuel injector fuel injection stability have great impact, making injector easily lead to fluctuations in fuel injection, high pressure fuel pipeline Zhongshi a pressure wave, the pressure wave in high-pressure pipeline in return oscillation, in the next cycle Fluctuations will have the effect of weakening or superimposed. Thus, the fuel-air particles emitted uneven, a second-or multiple-jet spray, which did not fully burn, the deterioration of the economy, the driving force of the drop, thermal efficiency, emissions increase.

Traditional mechanical fuel injection system of the main injector is subject to the impact load, the load through the adjustment of fuel injection and governor earlier this oil amended, but can not be achieved precise control.

Two kinds of systems diagram of the system compared shown in Figure 4, the performance comparison and analysis as shown in table 2.
Electronically controlled high-pressure common-rail fuel injection system of high pressure pipeline, the pressure is always maintained at a constant comparison to the extent that this is because for the pulse of hydraulic pumps in the common rail of the volume increases, a resonant effect, so that the pressure fluctuations Reduce and weaken, when hydraulic changes, by the pressure regulator works, the fuel injector will adjust to the more constant pressure.



Electronically controlled high-pressure common-rail fuel injection system of the fuel injector is controlled by multiple factors, fuel injection control of the basic load factors (the throttle opening of that), speed, temperature, oil temperature and the temperature into and fuel oil "The oxygen content in exhaust gas and how much. Determine the volume of fuel injection at the same time, by the ECU control electromagnetic valve to open the length of time to determine the size of each injector.

Electronically controlled high-pressure common-rail fuel injection system is characterized by: injection timing and fuel injection control of mutual independence, injection pressure and duration of fuel injection engine load and speed from the impact of the injection pressure of the tank, fuel injection And the starting point of injection are free to adjust to achieve the injection timing, fuel injection and injection rate of the optimal control; jet spray reliable and high pressure, to achieve a variety of laws, such as fuel injection. These characteristics of the diesel engine to achieve efficient, clean, low noise of the combustion process played a significant role.

Electronically controlled high-pressure common-rail fuel injection system has the advantages of flexible adjustable injection pressure at different load and speed can determine the best injection pressure. At the same time as the injection is achieved, the fuel injector and injection rate of the optimal control, improved as a result of the diesel combustion process and reduce the exhaust particles and NO-X emissions and reduce the combustion noise. Besides its fuel economy improvements are also very obvious. At present, controlled high-pressure common-rail fuel injection system is the development trend of higher jet pressure (200 MPa), a smaller jet-straight 41 (0.11 ~ 0.13 mm), a shorter response time (0.1 ms), lower power Consumption (using piezoelectric crystal injector) and function better software. Electronically controlled high-pressure common-rail fuel injection system is the inadequacy of the system is more complicated; In order to achieve precise control, the accuracy of the sensor higher pressure common-rail with the continuous improvement of the various components of the Common Rail system performance requirements Increasingly harsh. In addition, the power to control common-rail fuel injection system, the need for engine structure corresponding improvement, especially on the cylinder head design. The above decision of the electronically controlled common-rail fuel injection system of relatively high cost.
4, electronically controlled fuel the development of common rail technology

Electronic Fuel technology is now common rail diesel and gasoline engines of the major trends, but in the use of new technologies in the process, according to the use of different engine characteristics, making electronically controlled common-rail fuel the use of technology in different conditions, with the The matching system on the engine there is still great room for development, particularly in the common rail technology research and development direction.

(A) common rail technology research and development hot spots

How to solve the constant high-pressure common rail high pressure system sealed the issue.

How to solve the high-pressure common rail system tracks the pressure of the CPC tiny fluctuations caused by uneven injection of the issue.

How to solve the high-pressure common rail systems have MAP (3-D control data sheet) optimization problem.

How to solve the micro-structure, high-frequency electromagnetic-off valve design and manufacturing process of the key technical problems.



(B) common rail technology to promote environmental protection

High-pressure common-rail system is currently the most advanced fuel injection system, the internal combustion engine industry was recognized as one of the three major breakthrough, it can have different conditions to 120 MPa pressure on the stability of the jet spray controllable, so that the engine condition Combustion achieve the best conditions, greatly optimize performance, emissions of harmful components further reduced. High-pressure common rail diesel system is to meet European Ⅱ, the European Ⅳ Ⅲ, and even the European emissions regulations, the ideal fuel injection system. Common Rail Diesel technology helps to reduce exhaust emissions, reduce noise, fuel consumption, and so on. It is conducive to environmental protection of the Earth, but will also promote the diesel engine industry, automobile industry and related industrial development.