Seal means for isolated ground O.sub.2 sensor

In an oxygen sensor having a solid electrolyte member located in a metal shell and a terminal member located in a sleeve, said sleeve being attached to the metal shell to define a reference chamber between said solid electrolyte member and said terminal member, said terminal member retaining first and second contact leads which connect the solid electrolyte member to a controller and third and fourth contact leads that connect a heater associated with the solid electrolyte member with said controller, said first, second, third and fourth contact leads extending through said sleeve, the improvement in the sealing of said reference chamber from the surrounding environment comprising:

• an insulator ring and a sealing ring located between said metal shell and solid electrolyte member for sealing said reference chamber from the communication of exhaust gases when said sensor is located in an exhaust pipe;
• a groove located in said metal shell;
• a crimped surface extending from said sleeve and located in said groove, said crimped surface establishing a seal to prevent communication of air and water into said reference chamber;
• a porous filter located adjacent said terminal member;
• and
• a rubber gasket located between said porous filter and said sleeve, said first, second, third and fourth contact leads passing through said rubber gasket and said porous filter, said first and second contact leads being connected to said solid electrolyte member and said third and fourth contact leads being connected to said heater in said reference chamber, said rubber gasket axially biasing said porous filter into continual engagement with said terminal member, said porous filter having sufficient resiliency to engage said sleeve and said first, second, third and fourth contact leads to form a barrier to assure that only dry environmental air is presented to the reference chamber by preventing the entry of water into said reference chamber is presented with substantially dry environmental air, said heater maintaining said reference chamber above a present temperature such that changes in the oxygen content in the exhaust gases as compared to oxygen in the reference environmental air cause ions to flow in the electrolyte member, said changes in ion flow being presented to said controller through said first and second contact leads to accurately indicate an operational parameter of an engine as defined by exhaust gases.