Abstract
An engine vibration and noise signal being applied for the engine combustion assessment contains also information on: a valve clearance, head gasket damage and wearing out of elements of a vehicle drive system. As the engine mileage increases the wearing out of driving system elements also increases, and in consequence the characteristics of vibration and noise generated by individual sub-assemblies are changing. Diagnosing of defects can be performed on the grounds of the model-based vibroacoustic signal by comparing the measured signal with this model. However, this model should be adapted after each changes of driving system elements and after each engine overhaul. Thus, it should be easily and fast automatically identifiable. Methods of generating the base model and its identification were proposed. The model based diagnostic method was verified – in the paper - on the example of the engine exhaust valve defect. DOI: http://dx.doi.org/10.5755/j01.mech.19.3.4658
Highlights
The purpose of modelling the engine should be clearly stated
This work is dedicated to the development of the diagnostic model, which will enable one to find out the selected mechanical defects of the engine
The onboard diagnostics (OBD) system in a majority of cases does not consider this defect as a fault since it is masked by the engine control system [2, 3]
Summary
This work is dedicated to the development of the diagnostic model, which will enable one to find out the selected mechanical defects of the engine These defects generate changes in the vibroacoustic signal characteristics. Investigations carried out on spark ignition 4cylinder engines: Fiat Punto, Renault K7J and Ford Fiesta indicate that a part of vibration responses is of a random character and has a broad amplitude spectrum, while other responses are distinctly resonant. These first ones are characteristic for responses for the exhaust valve closing, where vibrations from cycle to cycle of the engine operation are not repeatable. The base model takes into account the influence of the responses of all elements of the drive system
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