Capacitance-type fuel sensor for sensing methanol in methanol-mixed fuel

Claim 1

A fuel sensor for sensing a mixing ratio of a mixed fuel, said fuel sensor comprising: a housing; a structure disposed within said housing, said structure having a fuel passage formed therethrough; an electrode assembly disposed within said housing and secured to said structure, said electrode assembly including paired electrodes which have respective probe portions exposed to said fuel passage; an integrated circuit board arranged within said housing and on which an output control circuit is disposed, said output control circuit issuing an amplified voltage output which varies in accordance with a small information signal applied to an input portion of said output control circuit; at least two fastening screws connecting said integrated circuit board to said structure to form a tight mechanical connection therebetween, said fastening screws being constructed of electrically conductive material; wherein said fastening screws have respective upper portions directly contacting mutually insulated sections of said input portion of said output control circuit, and respective lower portions directly contacting said paired electrodes, respectively, wherein each of said probe portions of said electrode assembly is entirely covered with an electrically insulating film, wherein one of said probe portions is a cylindrical conductive solid member and the other probe portion is a cylindrical conductive hollow member and concentrically surrounds said solid member, and wherein said electrode assembly is so arranged that said probe portions extend perpendicular to a longitudinal axis of said fuel passage along which said mixed fuel flows.