Performance Optimization Of Oil Pump For Automotive Engine

Internal cycloid gear pump has the merits of small size, light weight, strongsuction, low noise, small flow pulsation etc, and it is widely used in small and mediumpower engines. However, due to the complex shape of tooth profile, modeling andprocessing are often difficult. In addition, flow pulsation and volume efficiency are the twoimportant factors to evaluate the oil pump, oil pump design parameters and oil pumpinternal fluid flow characteristics are closely related to how superior they are. A highquality oil pump should have the characteristics of high volume efficiency and low flowpulsation.The tooth profile of traditional cycloid rotor is cycloid-arc type，the profiles ofdedendum and addendum of outer rotor are both arcs，which is linked by chamfer. Sothere exists a gap, which can generate oil trapping and impact, have a bad influence onvolume efficiency and pressure pulsation. A new type of rotor is found after searchingmany documents and papers, whose tooth profiles are consist of epicycloid andhypocycloid, which can improve oil trapping better. Based on the principle of rotorgeneration, a new structure is proposed. The tooth profile is equidistant curve of curtatehypocycloid.According to the above question, this paper makes intensive study by using themethod of combining theoretical analysis with experimental simulation, and provides anew method for oil pump design.Firstly, the forming principle of a common cycloid pump rotor tooth profilecurve is analyzed, and the basic structure parameters of rotor are determined. According tothe forming method of dual-cycloid rotor, one tooth profile of rotor is obtained, and itsconjugate curve is obtained by considering principle of gear engagement. Based on thetooth profile equations of new rotors, structure parameters of rotor are analyzed, which canhelp engineers make use of the rotor better. Based on3D modeling software UG, rotor parameterized modeling module isdeveloped, and the process of how to further develop the UG by using the vb.net and GRIPlanguage is introduced in detail.With the target of Maximum displacement of oil pump unit volume, the oil pumpdeveloped in this paper is optimal designed by considering some engineering practice andclassical theory. The models of common rotor and dual-cycloid rotor are built by using thedeveloped UG module, and the oil pump internal fluid3D model is derived. Pump fluidcharacteristics is analyzed by using Pumplinx which is a professional software for pumpresearch. Based on the result analyses, the influence of two kinds of rotor on pumpperformance is obtained, such as internal flow pulsation, pressure fluctuations. Theinfluence factors are obtained. Analyzing the oil pump cavitation phenomenon formingconditions at high rotation speed, and the problem of volume efficiency changing withengine speed is well explained.Finally, oil pump comprehensive performance test-bed is built and the pumpcomprehensive performance test is finished. Based on the test results, oil pump flowcharacteristic and volume efficiency changes are analyzed. The accuracy of the simulationresults is verified by comparing the numerical calculation results and the simulation results.Meanwhile, durability test is taken in the durability test-bed, and the experimental resultsshow that the design prototype completely reaches the standard service life, whichvalidates the feasibility of design procedure and develop method.