Gas sensor
A gas sensor includes an element body having an oxygen ion conductive solid electrolyte layer and internally provided with a measurement-object gas flow section that introduces a measurement-object gas and allows the gas to flow; a measurement-object gas-side electrode disposed in a portion of the element body, the portion being exposed to the measurement-object gas; and a reference electrode disposed inside of the element body. Let A [μA] be a limiting current when oxygen is pumped from the surroundings of the measurement-object gas-side electrode to the surroundings of the reference electrode with the measurement-object gas introduction section, and B [μA] be a limiting current when oxygen is pumped from the surroundings of the reference electrode to the surroundings of the measurement-object gas-side electrode with the reference gas introduction section, then a ratio A/B is greater than or equal to 0.005.
1. A gas sensor comprising:
an element body having an oxygen ion conductive solid electrolyte layer and provided with a gas introduction port through which a measurement-object gas flows to a measurement chamber;
a measurement electrode disposed on an inner surface of the measurement chamber;
a measurement-object gas-side electrode disposed with respect to a portion of the element body so as to be exposed to the measurement-object gas;
a reference electrode disposed inside of the element body;
a porous protective layer that covers part of the element body and allows the measurement-object gas to flow to the measurement-object gas-side electrode with a first predetermined diffusion resistance;
a reference gas introduction section that has a reference gas introduction layer, and introduces a reference gas serving as a reference for detection of a specific gas concentration in the measurement-object gas, and allows the reference gas to flow to the reference electrode with a second predetermined diffusion resistance;
a measurement pump cell that detects the specific gas concentration in the measurement-object gas based on a pump current when pumping oxygen in surroundings of the measurement electrode based on an electromotive force generated between the reference electrode and the measurement electrode;
a reference gas adjustment pump cell that carries an oxygen pumping current between the reference electrode and the measurement-object gas-side electrode, and pumps oxygen from surroundings of the measurement-object gas-side electrode into surroundings of the reference electrode,
wherein amounts of the first predetermined diffusion resistance and the second predetermined diffusion resistance determine a ratio A/B, wherein A[μA] is a limiting current when oxygen is pumped from the surroundings of the measurement-object gas-side electrode to the surroundings of the reference electrode with the porous protective layer exposed to an atmosphere having an oxygen concentration of 1000 ppm, and B[μA] is a limiting current when oxygen is pumped from the surroundings of the reference electrode to the surroundings of the measurement-object gas-side electrode with the reference gas introduction section exposed to an air atmosphere, and wherein the ratio A/B is predetermined to be greater than or equal to 0.005.
2. The gas sensor according to claim 1 ,
wherein the ratio A/B is greater than or equal to 0.4.
3. The gas sensor according to claim 2 ,
wherein the limiting current A is 1 μA to 10000 μA.
4. The gas sensor according to claim 2 , wherein the limiting current B is 8 μA to 200 μA.
5. The gas sensor according to claim 2 ,
wherein let C[mm 2 ] be an area of the measurement-object gas-side electrode, and D[mm 2 ] be an area of the reference electrode, then the area C is greater than or equal to 1.0 mm 2 , the area D is greater than or equal to 0.5 mm 2 , and a ratio C/D is greater than or equal to 1 and less than or equal to 20.
6. The gas sensor according to claim 5 ,
wherein the area C is less than or equal to 15.0 mm 2 .
7. The gas sensor according to claim 5 ,
wherein the area D is less than or equal to 4.0 mm 2 .
8. The gas sensor according to claim 1 ,
wherein the ratio A/B is less than or equal to 125.
9. The gas sensor according to claim 8 ,
wherein the limiting current A is 1 μA to 10000 μA.
10. The gas sensor according to claim 8 ,
wherein the limiting current B is 8 μA to 200 μA.
11. The gas sensor according to claim 8 ,
wherein let C[mm 2 ] be an area of the measurement-object gas-side electrode, and D[mm 2 ] be an area of the reference electrode, then the area C is greater than or equal to 1.0 mm 2 , the area D is greater than or equal to 0.5 mm 2 , and a ratio C/D is greater than or equal to 1 and less than or equal to 20.
12. The gas sensor according to claim 11 ,
wherein the area C is less than or equal to 15.0 mm 2 .
13. The gas sensor according to claim 11 ,
wherein the area D is less than or equal to 4.0 mm 2 .
14. The gas sensor according to claim 1 ,
wherein the limiting current A is 1 μA to 10000 μA.
15. The gas sensor according to claim 1 ,
wherein the limiting current B is 8 μA to 200 μA.
16. The gas sensor according to claim 1 ,
wherein let C[mm 2 ] be an area of the measurement-object gas-side electrode, and D[mm 2 ] be an area of the reference electrode, then the area C is greater than or equal to 1.0 mm 2 , the area D is greater than or equal to 0.5 mm 2 , and a ratio C/D is greater than or equal to 1 and less than or equal to 20.
17. The gas sensor according to claim 16 ,
wherein the area C is less than or equal to 15.0 mm 2 .
18. The gas sensor according to claim 16 ,
wherein the area D is less than or equal to 4.0 mm 2 .
19. The gas sensor according to claim 1 , wherein
a porosity of the porous protective layer is greater than or equal to 20% and less than or equal to 60%, and
a porosity of the reference gas introduction layer is greater than or equal to 15% and less than or equal to 50%.
20. A gas sensor comprising:
an element body having an oxygen ion conductive solid electrolyte layer and provided with a gas introduction port into which a measurement-object gas flows and a measurement-object gas distribution section that communicates with the gas introduction port and a measurement chamber;
a measurement electrode disposed on an inner surface of the measurement chamber;
a measurement-object gas-side electrode disposed in a portion of the element body so as to be exposed to the measurement-object gas;
a reference electrode disposed inside of the element body;
a porous protective layer that covers part of the element body and allows the measurement-object gas to flow through the gas introduction port into the measurement-object gas distribution section in which the measurement-object gas-side electrode is disposed, the measurement-object gas flowing to the measurement-object gas-side electrode with a first predetermined diffusion resistance;
a reference gas introduction section that has a reference gas introduction layer, and introduces a reference gas serving as a reference for detection of a specific gas concentration in the measurement-object gas, and allows the reference gas to flow to the reference electrode with a second predetermined diffusion resistance;
a measurement pump cell that detects the specific gas concentration in the measurement-object gas based on a pump current when pumping oxygen in surroundings of the measurement electrode based on an electromotive force generated between the reference electrode and the measurement electrode;
a reference gas adjustment pump cell that carries an oxygen pumping current between the reference electrode and the measurement-object gas-side electrode, and pumps oxygen from surroundings of the measurement-object gas-side electrode into surroundings of the reference electrode,
wherein amounts of the first predetermined diffusion resistance and the second predetermined diffusion resistance determine a ratio A/B, wherein A[μA] is a limiting current when oxygen is pumped from the surroundings of the measurement-object gas-side electrode to the surroundings of the reference electrode with the porous protective layer exposed to an atmosphere having an oxygen concentration of 1000 ppm, and B[μA] is a limiting current when oxygen is pumped from the surroundings of the reference electrode to the surroundings of the measurement-object gas-side electrode with the reference gas introduction section exposed to an air atmosphere, and wherein the ratio NB is predetermined to be greater than or equal to 0.005.