Process Control And Optimization On Finish Machining Of Engine Cylinder Hole

As one of the core components of car, the quality of engine directlyaffects the hole dynamic performance of car. The most direct approach toimprove the engine’s fuel efficiency and decrease engine’s friction loss isto improve the engine’s geometry accuracy. Boring and honing are thetwo important processes in the machining of engine cylinder hole.Dimensional accuracy and form tolerance generated in fine-boringprocess directly determines the engine’s performances. The sequentialhoning can not only remove larger allowance, but also can effectivelyimprove block hole’s dimensional precision, geometrical accuracy andsurface quality compared to other finish machining, therefore it is widelyused as the finish machining of engine cylinder block.Take a car-maker’s B12engine cylinder block as example, the mainaim is to solve the problem of engine cylinder hole’s dimension andshape control. The approach to control and optimize the hole shape isstudied to reduce the friction work of hole-piston friction pair. Thedesirable cylinder hole shape minimizing the work is obtained throughthe establishment and simulation analysis of the hole-piston friction pair model. The honing trajectory distribution law is revealed and a method toimprove the uniformity of the distribution is developed throughreconstruction of the honing trajectory and the transformation betweenthe distribution and the material removal amount. The computation of thecylindricity verifies that this method effectively improves the shapeaccuracy. A boring-coordinated methodology is also developed toimprove the hole shape and the dimension accuracy using various feed,considering the process equipment and the system condition. Threeaspects are included:Firstly, the simulation computation of the hole-piston friction pair’sfriction work is completed. Through the establishment of the simplifiedmodel of the hole-piston friction pair and the design of three differentblock hole shape, say straight, drum-shaped and cone, whose averagediameter are kept equal, the effect of the hole shape on the friction workis revealed by means of finite element analysis. The result shows that theideal straight-shaped hole results in the minimum friction work regardlessof the thermal deformation. Thus the hole precision machining should bedevoted to reducing the roundness and cylindricity.Secondly, the distribution law is determined and the influence of themotion parameters on the distribution is obtained through thereconstruction and analysis of the3D and2D honing trajectory. Theconversion relation between the distribution and the material removal rate is also established, then a method is developed to improve the shapeaccuracy. The computation of the cylindricity quantitatively verifies thatthis method can effectively improve the shape accuracy of cylinder hole.The simulation results show that honing head with dislocated-mountedhoning stone can efficiently overcomes the defect of uneven trajectorydistribution, therefore enhance the level of machining quality.Finally, a boring-coordinated control method is developed based onthe simulation of the cylinder boring trajectory and the analysis of thehole boring deformation by combining with the processing of cylinderhole’s precision machining data. The dimension-matching design of thefore-and aft process of the cylinder hole precision machining is proposedconsidering the boring’s better controllability than honing,. The boringhole shape is fixed to match the honing material removal rate, thereforemending the shape, improving the roundness and cylindricity, andenhancing the quality of the plateau honing net vein through theoptimization of the boring micro-programs. The experiments andstatistical analysis of the measured data prove that this optimization iseffective and feasible to improve the performance of the finishingmachining of cylinder hole.In conclusion, the friction work of the hole-piston friction pair issimulated and analyzed, and the influence of different cylinder holeshapes on the friction pair is evaluated. The3D and2D honing trajectories are reconstructed and the distribution law, as well as thedevelopment of a quantitative control method to improve the shapeaccuracy, are revealed. At last, a boring macro-program is revised tocoordinate the fore-and-aft process of cylinder hole finish machining torealize the machining accuracy using the vari-feed boring of fix the holeshape. This method can be used for controlling the finish machiningprocess too of optimize the cylinder hole. This study provides thetheoretical basis and technical approach to achieve the performance offinish machining of auto engine cylinder hole.