Design And Research On A Flow Detection System For FAI Electronic-controlled Injection Unit Based On Volume Method

In the electronically controlled fuel injection system,the ECU obtains the actual working condition of the engine by the signals of the various types of sensors.According to the analysis results of the ECU,the best fuel injection quantity is obtained and the injection pulse signal is sent to control the injection quantity of the injection unit.In order to realize the accurate control of the fuel injection amount and the air-fuel ratio,it is necessary to obtain the relationship between the actual fuel injection amount and the injection pulse width of the injection unit.Aiming at the further research and development of FAI technology system,this paper studies and designs a detection platform that can accurately measure the flow characteristics of FAI injection unit.The detection platform is built based on the volume method,and achieves the intelligent detection process with the photoelectric switches and microcontroller unit,so that the batch detection of the ejection unit can be realized.First of all,the flow detection system is built for the injection unit based on the principle of volumetric method.The single injection amount of the unit is obtained by measuring the time consumed by injecting a certain amount of fuel at a constant pressure state.The whole system is divided into three modules according to the functional division: the measurement module,the detection control module and the host computer module.On the measurement module part,the design of the metering level control and the metering unit control are mainly introduced,and the verification of the metering unit is carried out according to the relevant standard.In the part of the detection control module,the logic control design of the flow detection is introduced,including the calibration process and the logic design of the detection process.Secondly,in the host computer module,the human-computer interface software is designed by LabVIEW,and communication with the next crew is achieved through the CAN bus.According to the usage frequency and functional division of labor,the entire operation interface is divided into three parts: test interface,configuration interface and calibration interface,in which the test interface is a primary interface.The block diagram is designed with a master program and a four-function subroutine that uses the queue and the producer/consumer cycle data model to perform data processing during communication.The software is designed with two modes of manual detection and automatic detection,achieving the combination of product development and testing.Finally,in order to verify the stability and reliability of the designed detection system,the repeatability test of flow characteristic detection was carried out on the detection system.The results showed that the maximum coefficient of variation was 3.61% and the maximum relative difference was 2.59% under the various detection pulse width.As the maximum values of these two evaluation indicators are both less than 5%,the detection platform can be considered that the test data has a small dispersion and a high consistency.Since the fluctuation of the driving voltage affects the injection amount,the influence test of the driving voltage and the flow consistency test are carried out on the detection system.The voltage influence test is performed at the drive voltage of 10.7V,11.7V,12.7V,13.7V,14.7V and 15.7V,and the flow consistency test is completed under the typical injection pulse width 6800?s.The test results show that the driving voltage will affect the detection of the fuel injection quantity,but the stability of the detection system will not be affected.