Manutenção preditiva de lubrificantes em motores de combustão interna para aplicações leves

Abstract

Lubricant oil utilized on internal combustion engines is degraded throughout the use due to chemical reactions and contaminations and sooner or later it must be replaced. The speed and degree of deterioration depend upon the engine operating conditions, air temperature, air humidity and most importantly the oil formulation. The usual interval is conservative and it is common for these products to be replaced while they still have long remaining useful life. This leads to economic and environmental disadvantages. On the other hand it is also possible that lubricant becomes completely deteriorated before said interval is reached. The use of such degraded oil causes pronounced wear, increased fuel consumption and intense deposit formation within the engine. Predictive maintenance can be an interesting solution through application of onboard sensors for online and in situ monitoring of oil quality. Firstly, study of degradation processes and main parameters of lubricant quality is carried out. Secondly, several techniques are evaluated through review of related published works. The possible technologies include microacoustic sensors for viscosity measurement; solid-state and gas-phase sensors for verification of diluted fuel; electrochemical sensors which evaluate one or more properties according to their influence on electric parameters such as conductivity and permittivity; chemical recognition sensors which present selective sensitivity to specific components in the oil such as particular oxidation byproducts or contaminants; and optic sensors that verify light transmission through lubricant. The microacoustic and chemical recognition sensors were considered the most promising and are candidates for further studies. The number of devices available on the market that are capable of pinpointing the ideal oil change time is still small. Therefore, this field has great commercial potential. However, validation of any system requires thorough testing to attest its accuracy and reliability.