Study On Abnormal Sound Diagnosis Of Car’s Conditioning System

Air condition system can improve the ride comfort and also cause abnormal soundinside which can take passengers’ psychological reaction such as tension, be agitated,fatigue, inattention etc and even brings security hidden danger. Compressor is airconditioning system’s core component and compressor’ noise, vibration will be strictlycontrolled. Car’s matching is often not reasonable because compressor fixed in engine.If the measurements of reducing vibration and noise are not reasonable to airconditioning system and the whole car, it will cause abnormal sound.Experts at home and abroad made a lot of research to the principle of compressor,condenser, expansion valves, etc. But a set of relatively complete method is notinvolved.This paper puts forward a set of practical air conditioning system diagnosticmethods basing on the air conditioning system’s three factors: noise, vibration and pulse.This method had a successful application in the diagnosis of abnormal sound. Methodsinvolved in the content includes: the recognition of abnormal sound’s frequency,driving source search, path evaluation, the main path confirmation and abnormal soundreasons for, improving measures application and so on.The different diagnosis method and the experimental design of the analysis ofexperimental results are the difficulty and key. Experiment scheme design shouldconsider the various possibility of abnormal sound and the feasibility of the experiment.The most important for analysis of experimental results is experimental methodsselection and the extraction of useful information. In case one, the path influenced bycompressor vibration exists resonance is the cause of the abnormal sound. In case two,there are three aspects for the cause of the abnormal sound. Firstly, the engine mountdamping effect is poor. Second, expansion valves and evaporator exist abnormal soundfrequency resonance. The third, car exists abnormal sound radiation sources. At thesame time, we reduce the abnormal sound inside by the application of relevantmeasures.There are many signal analysis methods, which can be used to find out thedifferent causes and solve the problem. Analysis method specific include: interactivefilter confirmed by abnormal sound frequency; Harmonic analysis looking for abnormalsound source; Correlation analysis assessing impact path; value analysis, multiple process analysis evaluating noise impact path; the transfer function, order time analysisto find out resonance components; incremental analysis confirm abnormal soundcomponents; SONAH looking for abnormal sound source.