Seal means for isolated grounded 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 attached to the metal shell, the terminal member retaining first and second contacts on corresponding leads which connect the solid electrolyte member to a controller and third and fourth contacts on corresponding leads which connect a heater associated with the electrolyte member with the controller, said sleeve having an end with a plurality of openings for said leads and a central opening, said central opening allowing environmental air to be communicated to a reference chamber between the terminal member and solid electrolyte, the improvements comprising:

• a filter having a base member in radial engagement with the sleeve and an axial projection that extends from the base member through said central opening in said end of said sleeve into the surrounding environment, said filter allowing environmental air to be communicated to said reference chamber while excluding water;
• and
• a seal member having an inner and outer periphery, said outer periphery having a first series of pleats that radially engage said sleeve;
• said inner periphery having a second series of pleats that radially engage said axial projection on said filter, said seal member having a series of opening for said leads, said openings in said seal member having a third series of pleats that engage said leads to prevent environmental air from being communicated through said openings in said seal member to assure that environmental air presented to said reference chamber passes through said axial projection of said filer, said solid electrolyte member being exposed to exhaust gases from a vehicle while said reference chamber is presented with substantially dry environmental air through said filter, said heater maintaining said reference chamber above a preset 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 the controller through said first and second contacts, said seal member axially expanding in response to temperature while retaining said radial engagement with said sleeve and said axial projection on said filter to assure that only dry environmental air is communicated to said reference chamber.