Patent ID: 6136170
Filing Date: 2000-10-24
Classification: G01N

Abstract:
An exhaust as sensor for detecting a constituent which is contained in exhaust gas, the exhaust gas sensor comprising:a processing space;an oxygen concentration cell element comprising a solid electrolyte which has an oxygen-ion conductivity, and which has surface electrodes which have an oxygen permeability, one of the electrodes facing said processing space;an oxygen pump element for pumping oxygen into or out of the processing space in such a direction that the absolute value of a concentration cell electromotive force generated in the oxygen concentration cell element, decreases, the oxygen pump element comprising a solid electrolyte which has an oxygen-ion conductivity, and which has surface electrodes which have an oxygen permeability, one of the electrodes facing the processing space; anda heater element or heater elements for heating at least one of the oxygen pump element and the oxygen concentration cell element to a predetermined operating temperature of the sensor;wherein exhaust gas containing the constituent and oxygen is introduced into the processing space and into a space (hereinafter referred to as an opposed space) that is across the oxygen concentration cell element from the processing space, wherein the exhaust gas contacts with both sides of the oxygen concentration cell element;wherein the electrode facing the processing space on the oxygen pump element referred to as a first electrode, the electrode facing the processing space on the oxygen concentration cell element referred to as a second electrode, the electrode on the side of the opposed space on the oxygen concentration cell element referred to as a third electrode, oxidation catalyst activities of the first to third electrodes are adjusted so that the constituent in the exhaust gas introduced into the processing space and into the opposed space is consumed by the reaction thereof with oxygen in the exhaust gas with at least any one of the first to third electrodes acting as oxidation catalyst in at least one of the processing space and the opposed space and so that a difference in the consumption of the constituent which is caused by the reaction with oxygen occurs between the processing space and the opposed space;wherein the value of a current flowing through the oxygen pump element at the time when the absolute value of the oxygen concentration cell element electromotive force reaches the absolute value of a target value EC which is set within the range not more than 10 mV is taken as information reflecting the concentration of the constituent in the exhaust gas.