Ionic-conducting resistor for exhaust constituent sensors
A resistor-assembly includes a substrate, a heater, a resistor-element, and conductive-leads. The substrate is formed of a ceramic-material. The heater heats the resistor-assembly. The resistor-element is formed of an ion-conducting material that overlies the substrate. The conductive-leads are formed of a catalytic-metal that are in communication with a gas and in electrical contact with the resistor-element. The resistor-element is characterized by a resistance-value influenced by an oxygen-presence in the gas when the resistor-element is heated by the heater such that a resistor-temperature is greater than a temperature-threshold.
1. A resistor-assembly, comprising:
a substrate formed of a ceramic-material;
a heater that heats the resistor-assembly;
a resistor-element formed of an ion-conducting material that has a resistance-value which is influenced by an oxygen-presence in a gas when the resistor-element is heated by the heater above a temperature-threshold, wherein the resistor-element overlies the substrate, and wherein said substrate is located between the heater and the resistor-element; and
conductive-leads formed of a catalytic-metal that are in communication with the gas and in electrical contact with the resistor-element.
2. The resistor-assembly in accordance with claim 1 , wherein the resistor-element conducts oxygen-ions when the resistor-element is heated above the temperature-threshold.
3. The resistor-assembly in accordance with claim 2 , wherein the ion-conducting material includes an oxide of an element selected from a list that includes zirconium (Zr), cerium (Ce), uranium (U), and thorium (Th).
4. The resistor-assembly in accordance with claim 1 , wherein the ceramic-material includes an aluminum oxide.
5. The resistor-assembly in accordance with claim 1 , wherein the catalytic-metal includes platinum (Pt), palladium (Pd), rhodium (Rh), silver (Ag), nickel (Ni), gold (Au), and alloys thereof.
6. A gas-sensing-device suitable for use to control an internal combustion engine, said device comprising:
a substrate formed of a ceramic-material;
a heater which heats the device in response to receiving electrical energy;
a sensing-element in thermal communication with the heater, wherein the sensing-element detects oxygen in an exhaust-stream and outputs a sensing-signal based on a concentration of the oxygen in the exhaust-stream;
a resistor-element in thermal communication with the heater, said resistor-element formed of an ion-conducting material that has a resistance-value which is influenced by an oxygen-presence in a gas when the resistor-element is heated by the heater above a temperature-threshold, wherein the resistor-element overlies the substrate, and wherein said substrate is located between the heater and the resistor-element; and
conductive-leads formed of a catalytic-metal that are in communication with the gas and in electrical contact with the resistor-element, whereby the concentration of the oxygen in the exhaust-stream is indicated based on the resistance-value and the sensing-signal.
7. The device in accordance with claim 6 , wherein the device includes a controller in electrical communication with the heater, the sensing-element, and the resistor-element, said controller controls the electrical energy supplied to the heater, determines the resistance-value of the resistor-element, determines the sensing-signal of the sensing-element, and indicates the concentration of the oxygen in the exhaust-stream.
8. The device in accordance with claim 6 , wherein the resistor-element conducts oxygen-ions when the resistor-element is heated above the temperature-threshold.
9. The device in accordance with claim 8 , wherein the ion-conducting material includes an oxide of an element selected from a list consisting of zirconium (Zr), cerium (Ce), uranium (U), and thorium (Th).
10. The device in accordance with claim 6 , wherein the ceramic-material includes an aluminum oxide.
11. The device in accordance with claim 6 , wherein the catalytic-metal includes platinum (Pt), palladium (Pd), rhodium (Rh), silver (Ag), nickel (Ni), gold (Au) and alloys thereof.
12. The device in accordance with claim 6 , further comprising a protective-layer which overlays the resistor-element, the protective-layer including a cover-layer with an aperture extending therethrough such that the aperture is aligned with the resistor-element.
13. The device of claim 12 , wherein the protective-layer also includes a glass-seal within the aperture.
14. The device of claim 13 , wherein:
the cover-layer contacts the resistor-element and the substrate; and
the glass-seal contacts the resistor-element.
15. The device of claim 6 , wherein the conductive leads are exposed to a channel which contains the gas.