The Control Strategy And Software Development Of Pre-injection Base On High-Pressure-Common-Rail's Automotive Diesel Engine

Diesel engine is suitable for every aspect of society because of its high compression ratio,large torque and wide range of power.However,the high-pressure common rail system of most domestic diesel vehicles is almost under the environment of foreign technical monopoly.Therefore,the realization of its localization will be an important part of the development of domestic diesel engines.The fuel injection system can reduce the heat release rate of the pre-mixed combustion stage as much as possible,promote the diffusion combustion rate,shorten the whole combustion time,and make the combustion process timely and complete by controlling multiple injection.Realization of precise and flexible Control of fuel injection Law.It is of great significance to alleviate environmental pollution and meet the increasingly stringent.This article is based on the HT5 hardware platform,the strategy and software of injection combination(Due to the limitation of conditions,the maximum number of injection times is two pre-injection and main injection,a total of three injection),preinjection pulse width and timing of diesel engine under different working conditions are studied in order to continue improvement of Diesel engine Control system independently developed in Laboratory and promote the localization of common rail system.First of all,by analyzing previous experimental datas of changing the number of preinjection,the injection ratio and the injection time respectively under the operating conditions of start-up,idle speed and the normal operation of low-middle-load and partial speeds with the use of BOSCH control strategy,and find out the best injection mode and control parameters under different working conditions,and get the control MAP.It can provide reasonable MAP support for the realization of self-developed Common Rail System's software control and complete the pre-injection function.Secondly,the signal of crankshaft and camshaft sensor is processed to realize the program development of judging tooth,judging cylinder and the per-cycle's average rotation speed on the experimental prototype with 4+1 teeth of camshaft signal wheel.It also updates the analog-to-digital conversion MAP of the corresponding sensors such as cooling water temperature,throttle pedal opening and so on in the program,enable ECU to process the running information of the experimental prototype.After processing these sensor signals,design and writ the spray regime MAP,pre-release status word,the injection status byte and each pre-injection parameter MAP in the application layer of the software,and declare the injection mark bit in software application layer.Then through analysis the control of the "high,middle and low" position to the injection solenoid valve,to finish the design of the pre-injection driving process and realize the free control of the engine fuel injection by the software according to the operator's demand.Finally,the control model is established by using Simulink to realize the control of pre-injection process using MAP according to the change of engine speed and load.During the study,it is found that for multiple injection,because the interval between adjacent two injection is small,the previous injection release will cause a greater rail pressure fluctuation to the later injection.Therefore,it is a means to reduce this fluctuation by establishing Feedforward and PI feedback Control Strategy Model and achieve the simulation control of the AMEsim's Fuel injection system model.Then the control strategy is verified by state machine and control model,and collected two pre-injection signals at 1000 rpm and 10% load.