The Desing And Development Of Diesel Engine Urea-SCR Dosing Pump Control System Based On CAN Fieldbus

Compared with gasoline engine, diesel engine has incomparable advantages on powerperformance, economy, reliability, and especially low carbon dioxide emission. It has beenwidely used in large commercial passenger cars. However, more and more people pay attentionto the harm of exhaust pollution from diesel engines. The upcoming China National IVemissions regulations promote the domestic diesel engine manufacturers to find the effectiveways to control and reduce the discharge of pollutants. The selective catalytic reduction (SCR)technology is the best choice for heavy-duty diesel engines in China to reach the stage of ChinaNational IV emission standards. As an important part of the SCR system, urea metering pumpswill directly affect the performance of the SCR system. Due to the lack of the core technologyand the intellectual property on urea metering pump, domestic enterprises mainly import foreignurea metering pump, and afford expensive software and hardware costs. High installation cost ofSCR systems affects the popularization and application of diesel engines. Consequently, it isnecessary to develop a domestic SCR urea metering pump system．The core problem of meteringpump is to accurately control the amount of urea injection. In order to solve the above problem,this thesis will undertake the research of the urea metering pump control system based onController Area Network (CAN) bus.Firstly, based on the research of SCR system composition and the principle of urea meteringpump control system, diaphragm type is adopted as structure of urea metering pump controlsystem in order for the cost reduction of urea metering pump. Then, the hardware and softwareof the urea metering pump control system are developed according to the function of ureametering pump control system. The CAN bus communication is implemented in the ureametering pump control system, enable it to obtain urea dosing pump injection instruction andfeedback status information correctly, pressure buildup module is also completed, whichimproves the work efficiency and injection precision of the urea dosing pump. Finally, in orderto test the validity of urea metering pump control system, a calibration system is developed forthe calibration test of the metering pump. A large number of reliability tests and bench tests arealso performed. The test results show that the urea metering pump control system can exactlycontrol the amount of urea spray, and make the diesel engine emissions meet with therequirements of China National IV emissions regulations.