Oxygen sensor with heater

Claim 1

An oxygen sensor comprising: a tubular body of solid electrolyte having an elongate bore which is closed at one end of said tubular body and open at the other end, and further having reference and measuring electrodes on inner and outer surfaces thereof, respectively; a housing supporting said tubular body such that said outer surface thereof is exposed at said one end to exhaust gas, said housing maintaining said elongate bore in gas-tight condition with respect to said exhaust gas; and a bar-shaped heater inserted in said elongate bore in said tubular body, and comprising a heating resistor connected to an electric power source having a positive temperature coefficient, a ceramic body carrying said heating resistor so as to embed the heating resistor, and a pair of lead wires for connecting said heating resistor to an electric power source, said ceramic body having on its outer peripheral surface a pair of terminal pads connected to said heating resistor, an end portion of each of said lead wires being brazed to corresponding one of said terminal pads with a brazing material containing silver, said ceramic body further having on said outer peripheral surface a pair of equipotential members disposed outwardly of said pair of terminal pads, respectively, said equipotential members enclosing at least portions of the peripheries of the corresponding terminal pads which are opposite to each other.