Temperature compensated resistive exhaust gas sensor construction

Claim 1

An improved sensor of the type adapted for installation in an exhaust manifold or exhaust conduit for conveying exhaust gases from an internal combustion engine, the improved sensor being responsive to the partial pressure of oxygen in the exhaust gases to which the sensor is exposed and having an electrical characteristic which varies, when the sensor is at operating temperatures in the range from about 700° F. to about 1500° F., with the partial pressure of oxygen in the exhaust gases, the sensor comprising: a housing adapted for connection to the exhaust manifold or exhaust conduit of an internal combustion engine; a ceramic insulator having a forwardly projecting sensor element support portion and a rearwardly extending terminal portion received within the housing and positioned such that the forwardly projecting sensor element support structure is adapted to project into the exhaust manifold or exhaust conduit when the housing is connected thereto as adapted therefor, the forwardly projecting portion of said insulator including a thin-walled cavity and at least first, second and third passages extending from the bottom of the cavity to the rearward portion of the insulator; at least three electrical terminals each positioned within one of the three passages at the rearwardly extending terminal portion of the insulator; a pair of series-connected metal-oxide ceramic sensing elements supported within the cavity of the insulator, each of the sensing elements having at least two lead wires embedded therein, a lead wire from one of said pair of sensing elements being electrically connected to a lead wire of the other of the sensing elements, a second lead wire from said one of said pair of sensing elements passing through a first passage in the insulator, a second lead wire from the other of said pair of sensing elements passing through a second passage in the insulator, and a third lead wire passing through a third passage in the insulator, the third lead wire being electrically connected to the electrically connected lead wires of said one and the other of said pair of sensing elements, the lead wires in the first, second and third passages of said insulator being connected, respectively, to the three electrical terminal members received within the passages, the lead wires from the sensing elements being operative to support the sensing elements in the cavity of the insulator, the cavity having a depth sufficient to shield the sensing elements from the direct flow of gaseous products of combustion in the exhaust manifold or exhaust conduit; and said pair of sensing elements being exposed on all sides thereof to exhaust gases within the exhaust manifold or exhaust conduit, said one of said sensing elements having an electrical resistance which varies as a function of the temperature to which it is exposed and not substantially as a function of the partial pressure of oxygen to which it is exposed and the other of said sensing elements having an electrical characteristic responsive to both the temperature to which it is exposed and the partial pressure of the oxygen in the exhaust gases to which it is exposed when at a temperature within the range from about 700° F. to about 1500° F.