Inventors: Dickert FL, Forth P, Lieberzeit P, Voigt G, Marquardt KD
Patent Title: Oil quality sensor
Publication date: 2001
Publication number: WO/98/19156

Abstract: The chemical and/or physico-chemical determination of the ageing of a motor oil is very expensive and requires measuring methods which cannot be carried out on board a motor vehicle. The determination of only one condition parameter, for example the viscosity, only enables conditional statements to be made as concerns quality since conflicting effects may exist to varying degrees in this case. According to the invention, oil quality can be determined by means of a quartz coated with a sensitive layer. The sensitive layer has a surface or volume which is adapted to an oil component and is suitable for the repeated inclusion and precipitation of the oil component according to the concentration thereof. When the oil component is present, it is incorporated in the sensitive layer, such that the resonant frequency decreases via a mass effect or via an effective increase of the component thickness or mass. As the oil ages, the component incorporated in the sensitive layer decreases, such that the resonant frequency increases. A non-sensitive layer is used as a reference, by means of which the viscosity effect of the oil on the oscillation of the quartz and the variation in viscosity of the motor oil are determined as a second important oil quality parameter.
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