Patent ID: 8168054

Claim:
A gas sensing element comprising: first and second solid electrolyte bodies extending in a longitudinal direction and stacked on each other in a stack direction with a space therebetween for defining a measuring gas chamber; a diffusion resistance portion placed adjacent to the measuring gas chamber to admit measuring gases thereto under given diffusion resistance; a sensor cell mounted on the first solid electrolyte body for detecting a specified gas concentration of measuring gases admitted to the measuring gas chamber; an oxygen pump cell mounted on the second solid electrolyte body for adjusting an oxygen concentration in the measuring gas chamber; the sensor cell including a measuring electrode, formed on a surface of the first solid electrolyte body facing the measuring gas chamber, and a reference electrode formed on the other surface of the first solid electrolyte body in pair with the measuring electrode; the oxygen pump cell including an inner pump electrode, formed on a surface of the second solid electrolyte body facing the measuring gas chamber, and an outer pump electrode formed on the other surface of the second solid electrolyte body in pair with the inner pump electrode; the diffusion resistance portion and the inner pump electrode being placed adjacent to each other in the stack direction; and the diffusion resistance portion extending from the measuring gas chamber in a plane perpendicular to the stack direction from a position inward of external end walls of the inner pump electrode terminating at the external end walls of the inner pump electrode; wherein the measuring electrode is located in the measuring gas chamber at an area inside of the inner pump electrode.