Method for producing a subminiature 'micro-chip' oxygen sensor for control of internal combustion engines or other combustion processes, oxygen sensor and an exhaust safety switch

Abstract

A method of making a sub-miniature 'micro-chip' oxygen sensor is provided where multiple sensor elements are applied to a dielectric ceramic substrate consisting of a heater pattern, followed by a dielectric layer. Intermeshing electrodes are then applied either over the heater pattern/dielectric layers or on the opposite side of the substrate. The space between the intermeshing electrodes is filled with an n-type or p-type high temperature semiconductor which is covered by a porous protection layer. After singulation (dicing), the sensor element is assembled having conductors applied to the contact pads on the element and is packaged in an assembly for introduction to the exhaust stream of a combustion process. A large step-wise change in the resistance of the element takes place as a result of changes in oxygen content in the exhaust whereby one can determine if the exhaust is rich or lean for use in an engine management or combustion management systems for emissions control. A circuit is proposed to convert the change in resistance to a voltage signal to be used for control algorithms in engine or combustion control. Utilizing multiple units of the device for individual cylinder control of multi-cylinder engines is described. A method of using one embodiment of the invention for use as a safety switch is also revealed.