US 5,540,086 A · Oil deterioration sensor

Abstract

An oil deterioration sensor includes a housing, a substrate with a first capacitive plate mounted within the housing, a second capacitive plate mounted to the housing close to the first capacitive plate, and a total reference capacitor which includes an external fixed reference capacitor. The second capacitive plate is mounted to the housing such that oil freely circulates within a gap between the first and second capacitive plates thereby defining an oil deterioration sensor capacitor. The respective capacitances of the oil deterioration capacitor and the total reference capacitor provide an engine oil deterioration indication for the oil within the gap. The first capacitive plate is divided into a major sensing area, and a minor sensing area covering a relatively small portion of the total area of the first capacitive plate. The major sensing area and the second capacitive plate form the oil deterioration sensor capacitor. The total reference capacitor further includes an oil deterioration reference capacitor defined by the minor reference area and the second capacitive plate. The oil deterioration sensor further includes a temperature sensitive resistive element thermally connected to the substrate for providing a temperature adjustment to the engine oil deterioration indication, and circuitry utilizing the respective capacitances of the oil deterioration sensor capacitor and the total reference capacitor to generate the engine oil deterioration indication.

Claims20

Dependent claims

A capacitive oil deterioration sensor comprising:

a threaded metal housing having an inner end for threading into an oil pan of an automobile or other engine, said inner end including supports attached thereto;
a heat-conducting substrate mounted within said inner end and insulated from said housing, said substrate including an inner surface and an outer surface and a first capacitive plate on said outer surface;
a second capacitive plate mounted to said housing by said supports close to but apart from said first capacitive plate such that oil freely circulates within a gap between said first and second capacitive plates, said first and second capacitive plates defining an oil deterioration sensor capacitor;
a total reference capacitor including an external fixed reference capacitor, said oil deterioration sensor capacitor and said total reference capacitor providing an indication of viscosity of said oil within said gap;
and
a temperature sensitive resistive element thermally connected to said inner surface of said substrate for providing a temperature adjustment to said indication of viscosity in response to a temperature of said oil.

3 more elements

Dependencies are inferred from the claim text.

Oil deterioration sensor

Life of this patent

Oil deterioration sensor

Life of this patent

Abstract

Claims20