PROBLEMS OF IC ENGINES MECHANICAL FAULT DIAGNOSTICS

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PROBLEMS OF IC ENGINES MECHANICAL FAULT DIAGNOSTICS

Journal Title: Scientific Journals of Silesian University of Technology. Series Transport - Year 2011, Vol 2011, Issue 73

Abstract

The main purpose of modern, on board, diagnostic systems supervising electronic control systems is to check whether the ecological requirements are met. It means that the OBD system monitors catalyst and ignition system operations. However, the range of these activities is not sufficient for detection of engine faults formed during an exploitation. The assumed limits of the admissible variation of signals in the OBD systems are the reason of masking mechanical faults, which – at their early stages – are not visible for the system. Modern systems of on board diagnostics (OBD) are standard equipment of passenger cars allowing, first of all, to find faults which influence an emission of toxic components of exhaust gases. In practise, it is reduced to diagnostics of electronic systems responsible for basic functions of controlling car engine operations. Thus, currently used OBD systems usually allow only to find a simple fault of an individual element. This constitutes a significant limitation in a situation when some elements undergo an exploitation wear, but a wear of individual elements does not exceed their admissible value. Detection of early phases of mechanical faults e.g. by vibroacoustic methods, can significantly improve the currently used systems and prevent more serious damages having influence on emission quantity and work parameters of an engine. To this end, the application of an additional vibroacoustic diagnostic system supplementing the standard on board system in discovering faults of I.C. engines, can be very useful. Certain mechanical faults such as: increasing wear of valve seats and faces, shifting of timing gear phases, wear of a cylinder bearing surface even exceeding dimensions permissible for the given engine, in many cases – known from practice – do not trigger the reaction of the diagnostic system. The most often the application of algorithms of I.C. engines adaptive control systems is the reason of such situation. The engine adaptive control can lead to masking or adapting the developing errors. Mechanical faults and exploitation wear, especially in early development stages, are compensated by adaptive control systems as a result of the assumed admissible control ranges. Only, when more serious breakdown occurs, the process control is disturbed to such an extend that finding the failure becomes relatively easy since the system will switch to the breakdown mode operation.

Authors and Affiliations

Henryk MADEJ, Edward TRZENSIK

Keywords

silniki spalinowe diagnostyka uszkodzenia mechaniczne

EP ID EP86398
DOI -
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