Research On Fuel Supply Characteristics Of Electronic Unit Pump And Parametric Design Of Its Cam Profile

With the advantages of high injection pressure, small modifications to the existingengines, good oil adaptability and excellent system reliability, the fuel injection system ofelectronic unit pump (EUP) has become one of the ideal choices for high power dieselengines. EUP’s injection characteristics are closely related to its structure and the fuel flowin it. During fuel injection process the pressure wave in high pressure fuel pipe can reflectthe state information of the system. At present the change toward electronic control hasbeing coming for domestic diesel fuel system.The domestic current processing conditiondetermines that at the present stage EUP is the feasible and feasible way for the localizationof electronic control fuel injection system. In order to deeply analyse the influence of EUPstructure parameters on the flow characteristics in it, it is extremely needed to research anddevelop the EUP that is with independent intellectual property. The design of cam profile isone of the key technologies during the development of EUP fuel system. But the researchon cam profile design of EUP is seldom conducted, It is very important to explore its designmethod. Thus, Thus, with the main lines of EUP system fuel injection characteristics andsupply cam profile parametric design, in this work the researches are made which are on theinstability of EUP at low speed, its injection characteristics under different conditions,motion law of control valve stem and its effect on high pressure oil circuit, the influence ofEUP structure parameters on flow characteristics and the parametric design of supply camprofile.Firstly, in this paper the experimental system is built and the calibration method ofEUP system injection characteristics based on fuel pressure is provided. The results revealthat when control valve of EUP does’t work, the phase of fuel pressure peak backs off withincreasing speed.Then, using the test system, the research on low speed supply characteristics of EUP ismade. The results show that under low speed condition, there is obvious pressurefluctuation after the system establishes the pressure. So during the injection the needlecannot remain the stable open state. The pressure wave characteristics are analyzed. Thespecific location in the oil pressure waveform is indicates of the beginning and end ofcontrol valve closing, the opening of injector needle. The control valve movementlaw under high pressure condition is explored. It points out that there are rebounds when control valve stem firstly closes completely and firstly opens completely. On someconditions in the opening process of control valve, there will be the close trend.Then, the working principle and structure characteristic of BIT EUP is analyzed. Theinjection characteristics and its consistency is studied through experimental method. Theresults show that BIT EUP has good performance and repeatability. The fluctuation ofpressure and injection quantity is small for different pumps. The simulation model of BITEUP system is established. The calibration results indicate that the model can achievereasonable accuracy range. By means of the model the influence of factors on BIT EUPinjection characteristics is researched wihch include, structure parameters of control valve,the orientation between valve seat and pump body, oil line in the pump body and plungerdiamter. Finally, the reasonable choise range of different structure parameters is putforward.Subsequently, the cam main design criteria are summarized with performance,reliability, stability and manufacturability. With the constraint from design criteria theparametric design method of supply cam profile is studied using analytic method. And itsmathematical model is established whose parameters only include structural parameters andcharacteristic parameters with reflecting the design constraint.Finally, the matching study of cam profiles and EUP is done. The cam profile that canachieve the design goal is obtained. And the curvature radius is checked. The results showthat the cam gained and roller can always keep contacting in the concave arc segment andin the convex arc segment, the minimum curvature radius is over3mm.