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Diesel engine electronic control technology in this paper       2015-12-27   

Abstract: the paper introduces the development of diesel engine electronic control technology, control principle and application characteristic and the working principle of high pressure common rail technology, research direction and application prospect.

Key words: diesel engine electronic control technology; High pressure common rail technology; Application of the vision

1 development status and development trend of diesel engine electronic control technology

1.1 development of diesel engine electronic control technology

Diesel engine electronic control technology in the 1970 s, since the 1980 s, British Lucas company, Germany Bosch, mercedes-benz, gm of Detroit diesel engine company, cummins, caterpillar and komatsu, Japan isuzu motors are racing to develop new products and put on the market, in order to meet the increasingly stringent emission regulations.

Because of the diesel engine with high torque, the advanced age life, low fuel consumption, low emission characteristics of diesel engine become solve the automobile and engineering machinery energy topics and the most reliable method. So the using range of diesel engine is more and more widely, the number is increasing. At the same time to control the diesel engine's power performance, economic performance, emissions and noise pollution is becoming more and more demanding. Rely on the traditional mechanical control fuel injection system have been unable to meet the above requirements, also difficult to realize the injection volume, injection pressure and injection timing completely according to the requirement of the optimal condition of operation. In recent years, with the computer technology, sensor technology and the rapid development of information technology, the reliability of electronic products, capital, and so on various aspects volume can meet the requirements of diesel engine electronic control, and electronic control fuel injection very easy to implement.

In fact, CO and HC of diesel engine exhaust much less than that of gasoline engine, NOX emissions similar to gasoline engine, only exhaust particles is more, it related to the diesel engine combustion mechanism. Diesel engine combustion is a kind of heterogeneity, mixture formation time is very short, mixture formation and combustion process and crisscross together. Through analysis of diesel engine fuel injection law: spray into fuel atomization quality, the activities of the gas inside the cylinder and the combustion chamber shape are directly affect the progress of the combustion process and emissions by nature. Progress of diesel fuel injection pressure and atomization effect, use injection, injection, etc can effectively improve emissions.

After years of research and application of new technology, the present situation of the diesel engine is very different from the past. Modern advanced commonly used diesel engine electronic control injection, high pressure common rail, turbocharged inter-cooled technology, in weight, noise, smoke, etc has made significant breakthrough, achieved the level of gasoline engine. Along with the increasingly stringent emission control on international standards, such as European Ⅳ, Ⅴ standards promulgation and implementation, both in gasoline engine and diesel engine is facing serious challenges, the solution is one of the electronic control fuel injection technology. Now, the utility ratio of diesel engine electronic control technology in developed countries has reached more than 60%.

1.2 what is a diesel engine electronically controlled fuel injection system

The electronic control fuel injection and emissions of diesel engine is the diesel engine electronically controlled fuel injection system. Efi diesel injection system consists of sensors, ECU (computer) and the executive mechanism of three parts. Its task is to the electronic control of fuel injection system, implementation of fuel injection quantity and injection timing with the operating conditions of real time control. Adopt speed, throttle pedal position, injection time, cooling water inlet temperature, inlet pressure, fuel temperature, temperature sensors, such as type real-time detection parameters at the same time in the computer (ECU), stored and set the parameter value or parameter mapping (MAP), according to the optimal value or processed to calculate the target after the instruction to the actuator. Actuator control the fuel injection quantity according to the ECU instruction (oil rack position or electromagnetic valve closed duration) and injection timing (timing control valves open and close or electromagnetic valve closed starting point), at the same time of exhaust gas recirculation valve, such as preheating plug to control actuator, to achieve optimal operation of diesel engine.

1.3 the development trend of diesel engine electronic control technology

1.3.1 high injection pressure

To meet the requirements of emission regulations, diesel injection pressure mpa progress from 10 to 200 mpa. Such a high injection pressure can obviously improve the quality of fuel and air mixing, shorten the ignition delay, make the combustion more quickly and more completely, and control of combustion temperature, reducing emissions.

1.3.2 independent injection pressure control

Traditional diesel engine fuel supply system of the injection pressure is related to the speed of the diesel engine load. This feature for low speed, under the condition of partial load fuel economy and emissions. If the oil supply system has not depend on the speed and load of the injection pressure control, can choose the most appropriate injection pressure make the injection duration, the best ignition delay, make the diesel engine under various conditions of the lowest emissions and economy optimal.

1.3.3 improve diesel engine fuel economy

Users' specific fuel consumption of diesel engine is very concerned about. High injection pressure and separate injection pressure control, uniform small orifice and high injection pressure and other measures to reduce fuel consumption rate, to progress the use of diesel engine fuel economy.

1.3.4 independent fuel injection timing control

Injection timing directly affect the diesel engine piston top dead center is sprayed into the cylinder before the amount of oil, determine the peak value of cylinder explosion pressure and maximum temperature. Cylinder of high pressure and temperature can use to improve fuel economy, but has led to an increased NOX. And not depend on the speed and load of injection timing control ability, is in the key to achieve the best balance between fuel consumption and emissions.

1.3.5 variable injection control ability

Pre injection can reduce particle emissions, nor increase the NOX emission, but also improve the working condition of diesel engine cold start performance, to reduce the cold white smoke emissions and noise, improve the low-speed torque. But pre injection volume, injection and the time interval between the main injection at the request of the under different working conditions are not the same. Therefore, with variable injection control on diesel engine performance and emissions.

1.3.6 minimum oil control ability

Oil supply system with high injection pressure and the power of the diesel engine idle speed required amount of small oil control ability. After the oil supply system with pre injection ability will lower the ability to control small oil further. Due to mechanical engineering in the condition of diesel engine is very complex, idle condition frequently, and diesel engine electronically controlled fuel injection system is easy to achieve minimum oil control.

1.3.7 ability of rapid cut-off

Injection must be fast break at the end of the oil, if cannot fast break oil, under low pressure injection diesel will be due to inadequate burning smoke, increase the HC emissions. On the efi engine fuel injector high-speed electromagnetic switch valve fast break oil very easily.

1.3.8 reduce the drive torque impact load

Fuel injection system work under high pressure, both increased the uniform torque drive system need, also increased the impact load. Fuel injection system for smooth drive system's ability to load and unload, is a measure of the injection system. While the technology of high pressure common rail diesel engine electronically controlled fuel injection system technology greatly reduces the drive torque impact load.

2 the purpose of diesel engine electronic control technology and advantages

2.1 purpose

Optimizing performance, improving fuel economy use, emission control, make the diesel engine from idle to rated speed range can get the best working conditions, to prevent the possibility of dangerous operation condition, prolong the service life of parts.

2.2 the advantages

2.2.1 has multi-function automatic regulation performance

Engineering machinery with diesel engine operating condition is varied, and higher requirements on fuel consumption, emission and reliability. Automatic control technology is applied to the control system of diesel engine can realize multi-function automatic adjustment, to ensure that the diesel engine power performance, fuel economy, reliability and convenience manipulation such as performance into full play.

2.2.2 reduce quality, to reduce the compact size, the progress of diesel engine

For modern high speed diesel engine, due to the driver of the fuel injection pump torque is bigger, to design a compact and reliable fuel delivery advance automatic regulator is complex, and also on the general arrangement of diesel engine is more difficult. Using automatic control technology to solve the fuel delivery advance Angle automatically adjust the topic, not only can easily solve the above difficulties, and advances the compactness of diesel engine.

2.2.3 parts easy installation and connection, better maintainability

Adopt the automatic control system, the relevant parts size decreases (especially the fuel supply system), the installation site from the constraints of space position, the connection is simple, is advantageous to the diesel engine maintenance and repair.

2.2.4 extends the fault diagnosis, contact, etc

Adopt the automatic control system, it can be easily connected with a microcomputer, easily realize diesel engine performance test and fault diagnosis function, diesel engine running and testing data storage and transfer of title is solved, facilitate scientific management and use.

2.2.5 make diesel engine power output and load gets more accurate matching

With the rapid development of engineering machinery manufacturing technology, in order to progress of self-propelled construction machinery operation efficiency, used the efi engine, electric automatic control device, such as automatic transmission to self-propelled construction machinery in the job, can with the change of the load within a certain range automatically adjust the power output, power transmission, the diesel engine power output and load to get more accurate matching, give full play to the engineering machinery operation efficiency.

The characteristics of the 3 diesel engine electronic control technology

Diesel engine electronic control technology and the gasoline engine electronic control technology has a lot of similarities, the whole system is made up of sensors, electronic control unit and actuator of three parts. In electronic control injection is the main difference between diesel and gasoline engine, gasoline engine electronic control injection system is a control of air-fuel ratio (the proportion of gasoline and air), the electronic control injection system of diesel engine is by controlling the fuel injection time to adjust the size of the output of oil, and diesel engine fuel injection control is made up of the engine speed and the accelerator pedal position (gas, oil rod location). Diesel engine electronic control technology, there are two obvious characteristics: one is the diesel electric actuator is complex, the second is the diversification of electronically controlled diesel injection system.

3.1 diesel engine is a kind of dynamic mechanical thermal efficiency is higher

Diesel engine fuel injection has the characteristics of high voltage, high frequency, pulse. The injection pressure up to 200 mpa, the injection pressure of the gasoline engine more than one hundred times. The high pressure fuel injection system of the implementation of electronic control fuel injection quantity, is much more difficult. And diesel injection of injection timing accuracy requirement is very high, relative to the Angle of the diesel engine piston top dead center position than gasoline engine requirements correctly, this leads to the electric actuator of diesel spray is much more complex.

There are different forms of 3.2 as a result of the diesel injection system

The traditional diesel engine with inline pump, distribution pump, pump injector, such as single cylinder pump structure completely different system. Implementation of electronic control technology of the actuator is more complex, formed the diversification of diesel fuel injection system; While diesel engine oil amount, timing, would need to be integrated control of more parameters such as injection pressure, the difficulty of its software are also greater than gasoline engines.

The electronically controlled diesel fuel injection system is classified

The first is electronically controlled fuel injection pump technology, then developed the electric pump and high pressure common rail fuel injection nozzle technology, after the two technologies is now the main diesel engine electronic control injection technology. Electric pump nozzle technology of injection pressure is very high, up to 200 mpa, and pump and nozzle packed together, so only need a short high pressure oil guide part, pump nozzle system also can realize pre spray a small amount, the spray characteristics of the triangle, and adopt the sectional jet, which is very accord with the requirement of diesel engine (Volkswagen TDI engine is using this technique). But electric pump nozzle technology of injection pressure influenced by diesel engine speed, using the high pressure common rail accumulator system technology can solve the questions. The injection pressure is lower than the pump nozzle system, can achieve 160 mpa. Some companies took a fancy to it on any number of cylinders of the characteristic of engine fuel injection pressure regulation is very broad, gradually expand the scope of its use (the first to use high pressure common rail cars is alfa romeo 156 and Benz C level).

4.1 the first generation of diesel engine electronic control fuel injection system is also called the position control system, it use electronic servo instead of mechanical governor control adjustment for flattering sleeve position in order to realize the flow of oil. Its characteristic is to save the traditional fuel injection pump, high pressure tubing, fuel injector system, only on the rack or the movement of the sliding sleeve position is controlled by the original mechanical governor to computer control. This kind of technology has developed to the can control the timing and TICS in the process of the injection system at the same time.