Abstract: At least a portion of an oxygen sensor element support to which portion an oxygen sensor element directly contacts is constructed of an heat insulating material having very low thermal conductivity, so that the heat release from the oxygen sensor element is minimized.

Abstract: A process for forming a thin dense layer from a paste of powder in organic vehicle, comprises applying the paste onto a substrate by a screen printing technique, drying and sintering the applied paste under sintering conditions, and repeating the above procedure at least one more time, so as to yield a thin dense sintered layer which is longer in lifetime and more stable in quality than those obtained by known techniques.

Abstract: An oxygen sensing element of the type having a solid electrolyte oxygen concentration cell formed as a laminate of thin layers on a ceramic substrate in which a heater is embedded and end portions of lead wires are inserted. To enhance reliability of insulation between a lead wire through which heater current flows and lead wires connected to the concentration cell electrodes, the end portion of the heater lead wire is inserted into the substrate so as to make close contact with a terminal portion of the heater over substantially the entire length thereof and is completely shielded from environmental atmosphere by the substrate. Accordingly, even though a carbonaceous substance may be deposited on the substrate surface during practical use of the element, the possibility of heater current leaking of the concentration cell is obviated.

Abstract: A gas sensor having a gas sensing element, e.g. a solid electrolyte oxygen concentration cell, attached to a front end of a rod-shaped ceramic holder which is fitted in a tubular metal casing and a short rod-shaped ceramic plug fitted in a rear end portion of the tubular casing so as to leave a space between the rear end of the holder and the plug. Across the space, a plurality of lead wires attached to the sensing element extend through axial holes bored in both the holder and the plug. The space between the holder and the plug and the holes in the plug are filled with a hermetic sealant, which is preferably a lead glass solidified from molten state within the casing, to positively prevent gases subject to measurement from passing through the holes in the holder.

Abstract: A device having an oxygen sensing probe to be disposed in a combustion gas to detect actual air/fuel ratio values of an air-fuel mixture subjected to combustion. The probe is a combination of two oxygen concentration cells each having a porous solid electrolyte layer such as of zirconia, a porous measurement electrode layer on one side of the solid electrolyte layer and a reference electrode layer on the other side, with a shield layer thereon. Either the shield layers of the two cells or the solid electrolyte layers of the two cells are provided by a single layer which serves also as a substrate of the entire probe. The device includes DC power supply means for forcing a current to flow through the solid electrolyte of each cell thereby to cause oxygen ions to migrate through each solid electrolyte layer, from the reference electrode layer to the measurement electrode layer in one cell and reversely in the other cell.

Abstract: A method of detecting numerical values for air/fuel ratio of either a lean air-fuel mixture or a rich mixture supplied to, for example, a combustion engine by means of an oxygen sensor disposed in the exhaust gas. The sensor comprises a porous measurement electrode layer on one side of a porous solid electrolyte layer, e.g., of zirconia and a porous reference electrode layer on the other side with a shield layer thereon, so that the reference electrode layer communicates with the exhaust gas through pores in the sensor. Measurement is accomplished by keeping a DC current flowing between the two electrode layers to establish a reference oxygen partial pressure on the reference electrode side. The intensity of the current is made below a critical value above which an EMF generated by the sensor becomes substantially constant unless the air/fuel ratio changes across the stoichiometric ratio, and the direction of the current flow is chosen depending on whether the air-fuel mixture is a lean one or a rich one.

Abstract: An apparatus comprising a probe having an oxygen ion conductive solid electrolyte layer, a potentiometer and a DC power source connected to the probe. The probe comprises a porous and electronically conductive reference electrode layer on one side of the solid electrolyte layer, a similar measurement electrode layer on the other side of the electrolyte layer and a separation layer of an inactive material on the outer side of the reference electrode layer. The separation layer or the solid electrolyte layer, or both, has a porous structure and is formed such that the reference electrode communicates with an exterior atmosphere only through this porous structure, while either the separation layer or the electrolyte layer serves as a substrate of the probe. During measurement, the DC power source keeps a current flowing through the electrolyte layer between the two electrode layers to maintain a reference oxygen partial pressure at the interface between the electrolyte layer and the reference electrode layer.