Measurement and control of exhaust gas recirculation with an oxygen pumping device

Claim 1

An electrochemical device for measuring the percentage of exhaust gas recirculation (EGR) in an intake air and exhaust gas mixture of an internal combustion engine, said electrochemical device including: a generally planar first electrochemical pump cell including a relatively dense ZrO 2 platelet with porous platinum electrodes on two sides of said platelet; a first porous ZrO 2 layer deposited on one electrode of said first pump cell; a generally planar second electrochemical pump cell including a first porous platinum electrode, a second porous ZrO 2 layer and a second porous platinum electrode deposited successively on said first porous ZrO 2 layer; a second cell external circuit means coupled to said second pump cell for passing a constant current through said second pump cell so that said second electrode is biased positively causing a portion of the oxygen molecules inside said first porous ZrO 2 layer to be pumped out by said current flowing through said second pump cell; a first cell external circuit means coupled to said first pump cell for applying a constant voltage across said first pump cell so that the exposed electrode is biased positively, said constant voltage across said first pump cell being sufficient to cause substantially all of the remainder of the oxygen molecules inside said first porous ZrO 2 layer to be pumped out by a current flowing through said first porous ZrO 2 layer but less than that capable of disassociating CO 2 or H 2 O molecules; and a third external circuit means coupled to said first pump cell for measuring the current flowing through said first pump cell, said current being proportional to the percentage of O 2 inside said first porous ZrO 2 layer not pumped out by said second pump cell and also proportional to the percentage of O 2 in said intake air and exhaust gas mixture.

Claim 6

A method for measuring the percentage of exhaust gas recirculation in an intake air and exhaust gas mixture of an internal combustion engine including the steps of: forming a generally planar first electrochemical pump cell including a relatively dense ZrO 2 platelet with porous platinum electrodes on two sides of said platelet; depositing a first porous ZrO 2 layer on top of one of the electrodes of said pump cell; forming a generally planar second electrochemical pump cell including a porous platinum electrode, a second porous ZrO 2 layer and a porous platinum electrode deposited successively on top of said first porous ZrO 2 layer; passing a constant current through said second pump cell so that the exposed electrode is biased positively causing a portion of oxygen molecules inside said first porous ZrO 2 layer to be pumped out by the current flowing through said second pump cell; applying a constant voltage across said first pump cell so that the exposed electrode is biased positively, said constant voltage across said first pump cell being sufficient to cause substantially all of the remainder of the oxygen molecules inside said first porous ZrO 2 layer to be pumped out by a current flowing through said first porous ZrO 2 layer but less than that capable of disassociating CO 2 or H 2 O molecules; and measuring the current flowing through said first pump cell, said current being proportional to the percentage of O 2 inside said first porous ZrO 2 layer not pumped out by second pump cell and also proportional to the percentage of O 2 in said combined intake air and exhaust gas mixture.

Claim 7

A method for measuring the percentage of exhaust gas recirculation in an intake air and exhaust gas mixture of an internal combustion engine including the steps of: forming a generally planar first electrochemical pump cell including a relatively dense ZrO 2 platelet with porous platinum electrodes on two sides of said platelet; depositing a first porous ZrO 2 layer on top of one of the electrodes of said pump cell; forming a generally planar second electrochemical pump cell including a porous platinum electrode, a second porous ZrO 2 layer and a porous platinum electrode deposited successively on top of said first porous ZrO 2 layer; passing a constant current through said second pump cell so that the exposed electrode is biased positively causing a portion of oxygen molecules inside said first porous ZrO 2 layer to be pumped out by the current flowing through said second pump cell; applying a constant voltage across said first pump cell so that the exposed electrode is biased positively, said constant voltage across said first pump cell being sufficient to cause substantially all of the remainder of the oxygen molecules inside said first porous ZrO 2 layer to be pumped out by a current flowing through said first porous ZrO 2 layer but less than that capable of disassociating CO 2 or H 2 O molecules; and measuring the current flowing through said first pump cell, said current being proportional to the percentage of O 2 inside said first porous ZrO 2 layer not pumped out by second pump cell and also proportional to the percentage of O 2 in said combined intake air and exhaust gas mixture.