Some Lssues On Measurement And Evaluation Of Skirt Profile Of High-precision Piston

Piston is one of the key components of automobile's engine, its manufacturing precision may directly have influence on automobile's performancce. With the continuous improvement of the quality and output of automobiles in our country, the requirement of piston's manufacturing precision is higher and higher, and the measurement and evaluation of the high precision piston's skirt profile is one of the research contents in the manufacturing of high precision piston.Some issues on the measurement and evaluation of piston's skirt profile are studied in this thesis. On the basis of introduction of research situation of piston measurement at home and abroad and the operating principle of the multifunctional measuring instrument for cylinder's diameters and form & position errors, the evaluation of piston's skirt profile is researched. The evaluation models of piston's skirt cross section profile and axis section profile are built based on the technical requirements of piston and the manufacturing technique of piston's skirt, and the study on the dimension evaluation of piston's skirt is also done. Considering the special structure of piston's skirt and the characteristics of the measuring instrument, the issue relative to the meauring path plan for the piston's skirt is studied. Although the precision centering and tilting adjustment of the measured piston on the measuring instrument of the cylinder's diameters and form & position errors is done before measuring, there still exists the un-coincidence of the piston's axis and the turntable's axis. The center coordinates of each measured section of piston are calculated by using the least square circle method, and the coordinates the sampling points are transformed based on the coordinate translation and rotation principle. The characteristic parameters of piston's skirt profile are determined by using the least square method, and the theoretical models of piston's axis section are built on the basis of 3-spline interpolation method. Based on the theoretical research above, the evaluation program of piston's skirt profile was developed by Visual Basic 6.0 and 3D Cwgraph control of LabView 8.0, and The piston samples machined by the high precision piston lathe, developed by Zhongyuan University of Technology and Beijing Haipurunsen Science and Technology Co., LTD, were measured and evaluated, which may provide the basis for the lathe's further adjustment.