Research And Development Of On-Line Measuring Technique About Dimension And Shape Errors For Automobile Engine Cylinder Bore

The development of China's auto industry is in a fast rising channel at present.In order to improve working efficiency and service life of the engine,many enterprises have taken the errors of size and shape about the engine cylinder bore as an important target to control,and make them as a qualified basis.However,because of lacking on-line measurement equipment,some enterprises only measure aperture,and there are not roundness and cylindricity.Although advanced cylinder on-line measuring instruments are introduced to some enterprises,it is expensive and need to make corresponding improvements according to the production requirements of enterprises,which will increase the cost and affect the economic efficiency of enterprises seriously.In this paper,on-line measuring technique about dimension and shape errors for automobile engine cylinder bore is researched.Firstly,the development status of on-line measurement equipment,which is about size and shape errors of engine cylinder hole,are introduced.And some research results at home and abroad of evaluation algorithms in the aspects of shape errors are described.The positioning device,the lifting platform and measuring head of the measuring device are 3D designed,and error evaluation software is developed to deal with coordinate data.Secondly,according to the working principle of the on-line measuring device,the mathematical models of roundness,cylindricity are getting.There are four kinds of error evaluating methods,which are minimum zone method,least square method,minimum circumscribed circle method and maximum inscribed circle method.The objective functions of different error evaluating methods are obtained.By comparing the characteristics of various optimization algorithms,the genetic algorithm is selected and the best fitness functions are chose to obtain the optimal parameters' values of ideal circle center and ideal cylindrical axis.Finally,the coordinates of different measuring points of engine cylinder bore are achieved,and the analysis of the measured data is carried on by using MATLAB.The roundness error and the cylindricity are calculated,and the evaluation results of different optimization algorithms are compared.The errors caused by different factors,such as positioning,lifting platform,the installation of sensors and temperature,the rotation of the measuring head,are analyzed.The research on the evaluation technology of on-line measuring errors is completed eventually.