Substantiation of the method for diagnosing the ignition system of automobile petrol engines by exhaust gas toxicity parameters in individual cylinders

Abstract

It is known that the proportion of failures of the elements of the power supply system of automobile piston engines reaches 45% of all its failures, including 9% of cases are failures of the elements of the ignition system. An analysis of this statistics shows that spark plugs are most susceptible to wear, overheating and significant loading. The range of resource parameters of spark plugs offered by manufacturers within 10-60 thousand km aggravates the situation of timely replacement. It was revealed that the period for replacing spark plugs can be adjusted, since their guaranteed resource sometimes does not correspond to the declared one. It has been determined that the means used for diagnosing the ignition system (in the classic version: a motor-tester, a gas analyzer) do not allow to accentuate the load on a separate element and bring it to an extreme operating mode, in which hidden failures appear. The sensitivity and reliability of existing methods are at a low level, because Many factors influence the shape of the oscillogram, including interference in the measuring circuit and measurement errors, the need for frequent calibration of the measuring channels, which introduces a significant error in the diagnostic process. The purpose of the research is to increase the reliability of diagnosing the elements of the ignition system of automobile engines based on the analysis of toxicity parameters during selective sampling of exhaust gases in test modes. A method for troubleshooting and assessing the technical condition of the elements of the ignition system in test modes with selective sampling of exhaust gases is proposed, for the implementation of which a software and hardware complex for test diagnostics has been developed. On the basis of the developed methods, a methodology for the comprehensive determination of the technical condition of spark plugs in the engines of VAZ and GAZ vehicles was created based on the results of the analysis of the composition of exhaust gases on comparative nomograms. Scientific novelty: a mathematical model of the change in the secondary voltage depending on the spark interelectrode gap of the spark plug has been developed; the relationship between the breakdown voltage in the interelectrode gap of the spark plug and the air density in the chamber of the test device is established, where the most significant factor is the discrepancy between the interelectrode gap of the spark plug to its nominal value: the dependence of the parameters of the composition and content of harmful substances in the exhaust gases on the technical condition of the elements of the ignition system in individual engine cylinders. The practical significance of the work lies in the possibility of continuous monitoring of the elements of the ignition system by the test method, in particular the spark plugs of the ignition system, taking into account the individual contribution of each spark plug to the exhaust process and the content of toxicity parameters in the exhaust gases. Further research on this topic should be extended to other brands of cars, as well as gas engine installations with elements of automating the diagnostic process.

Keywords

• diagnostics
• test mode
• ignition system
• breakdown voltage
• spark gap
• toxicity parameters