| 摘要 |
PROBLEM TO BE SOLVED: To obtain an air-fuel ratio sensor element which can shorten the activation time of a sensor and whose thermal shock resistance due to a quick temperature rise is superior. SOLUTION: A first pair of electrodes 3, 4 are formed on the inside and the outside of a cylindrical tube 2 which is composed of a solid electrolyte and one end of which is sealed. A space part 5 is formed on the outside surface of the cylindrical tube 2. The circumference of the space part is coated with a ceramic insulating layer 7 which is formed by burying a heating element 6. A solid electrolyte layer 8 is formed so as to close the space part 5. A second pair of electrodes 9, 10 are formed in mutually opposite positions on the solid electrolyte layer 8. A diffusion hole 11 which is used to take into a gas to be measured is formed in the solid electrolyte layer 8. The space part 5 is filled with a porous ceramic. A space volume which excludes a ceramic filled substance in the space part 5 is set at 20×10-3 to 100×10-3 (mm3). The thickness of the solid electrolyte layer 8 is set at 100 to 350μm.
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