Improvement of diagnostics method of cylinder and piston groups of car engine

Abstract

The paper presents the results of improving the process of diagnostics of the tightness of the combustion chamber of gasoline engines relative to modern cars. The statistical hypothesis about the normal distribution of a random variable of compression is proved. The regression equation is obtained for a random variable of compression depending on the engine speed. The regression model also takes into account the number of valves per cylinder. The model of the diagnosis of the technical condition of the engine, namely the tightness of the combustion chamber is formalized. The range of diagnostic parameters for assessing the tightness of the combustion chamber of a gasoline engine of modern models is determined. Experimental studies on cars of different European and Asian brands are performed. Using a strain gauge measurement method with subsequent analog-digital conversion of the signal, measurements of diagnostic parameters were use. Experimental data processing was carried out using mathematical statistics methods. Using the method of regression analysis, a correlation between the amount of compression and the frequency of rotation of the crankshaft was established; the method of tolerant limits set the limit for the allowable amount of compression; using the theoretical methods of analysis, synthesis, modeling and Boolean algebra, the diagnostic process is formalized. A statistical model has been developed on the basis of on the improvement of the diagnostic method, which evaluates the technical condition of the cylinder-piston group and the tightness of the engine valves according to three diagnostic parameters: the difference in compression between the cylinders, the rate of increase in compression, the pressure of crankcase gases. It allows localizing malfunction of the cylinder-piston group and the tightness of the engine valves, as well as formalize the process of automatic installation of technical diagnosis.