US4228128A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Exhaust gas sensor having porous, metal-impregnated ceramic element
Assignee: Ford Motor Co
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Filing: 1979-03-19
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Granted: 1980-10-14
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Expires: 1999-03-19
Abstract
Abstract An improved sensor having a ceramic element that undergoes a change in an electrical characteristic in response to a change in the partial pressure of oxygen in a mixture of gases to which the ceramic element is exposed. Sensors of this type are used to detect the air/fuel ratio of mixtures supplied to internal combustion engines. Prior art sensors are characterized by little change in their respective electrical characteristics at low operating temperatures. A charge transfer material, platinum or platinum/rhodium is applied to the ceramic element to facilitate or make possible the electron transfers required for sensor operation at low temperatures. Platinum/rhodium alloy is the currently preferred charge transfer material. This alloy, which preferably is 90% platinum and 10% rhodium, reduces the minimum temperature of operation for the sensor as taught herein, and it also substantially eliminates vaporization loss of the charge transfer material.
Inventors
- 👤 Michael J. Esper
- 👤 Wells L. Green
- 👤 Stanley R. Merchant
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:29
CPC Classifications
H; H01; H01C; H01C7/00; H01C7/04; H01C7/042; H01C7/043; H01C7/045; G; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/12; Y; Y10; Y10T; Y10T436/00; Y10T436/20; Y10T436/207497; Y10T436/208339
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
277 words
An improved sensor of the type having a metal oxide ceramic element that undergoes changes in resistivity in response to variations in the partial pressure of oxygen in the gaseous medium to which the metal oxide ceramic element is exposed, the metal oxide ceramic element having electrodes in spaced apart relationship, the electrodes extending from the metal oxide ceramic element to permit the resistance between them to be sensed, and the metal oxide ceramic element being adapted to be immersed in the gaseous medium, wherein the improvement comprises: the metal oxide ceramic element is titania (TiO 2 ) and is porous to enlarge, as compared to a less porous material, the amount of titania element surface area exposed to the gaseous medium, and the titania element surface area has on it, and substantially throughout the volume of the titania ceramic element, a discontinuous charge transfer material comprising a metal having free electrons, whereby, the response time of the titania ceramic element is substantially reduced due to the presence of the charge transfer material, in the lower portion of the temperature range over which the titania ceramic element responds to variations in the partial pressure of oxygen in the gaseous medium; the sensor includes a second ceramic element less responsive to variations in the partial pressure of oxygen in the gaseous medium that is the first-mentioned ceramic element, and includes means for electrically connecting the first-mentioned ceramic element and second ceramic element in circuit such that output voltage changes from 33% to 66%, and vice versa, of applied voltage occur in less than about 300 milliseconds when the ceramic elements are at a temperature of about 350° C.
Claim 2
Dependent Claim
277 words
An improved sensor of the type having a metal oxide ceramic element that undergoes changes in resistivity in response to variations in the partial pressure of oxygen in the gaseous medium to which the metal oxide ceramic element is exposed, the metal oxide ceramic element having electrodes in spaced apart relationship, the electrodes extending from the metal oxide ceramic element to permit the resistance between them to be sensed, and the metal oxide ceramic element being adapted to be immersed in the gaseous medium, wherein the improvement comprises: the metal oxide ceramic element is titania (TiO 2 ) and is porous to enlarge, as compared to a less porous material, the amount of titania element surface area exposed to the gaseous medium, and the titania element surface area has on it, and substantially throughout the volume of the titania ceramic element, a discontinuous charge transfer material comprising a metal having free electrons, whereby, the response time of the titania ceramic element is substantially reduced due to the presence of the charge transfer material, in the lower portion of the temperature range over which the titania ceramic element responds to variations in the partial pressure of oxygen in the gaseous medium; the sensor includes a second ceramic element less responsive to variations in the partial pressure of oxygen in the gaseous medium that is the first-mentioned ceramic element, and includes means for electrically connecting the first-mentioned ceramic element and second ceramic element in circuit such that output voltage changes from 33% to 66%, and vice versa, of applied voltage occur in less than about 300 milliseconds when the ceramic elements are at a temperature of about 350° C.
Claim 3
Dependent Claim
191 words
An improved sensor according to claim 1 wherein the titania ceramic element is made from titania particles a substantial majority of which are of the rutile phase, 100% of the titania particles are smaller in size than 20 microns and a substantial majority thereof are smaller in size than 10 microns, and platinum is dispersed throughout the titania in the form of platinum particles deposited on the particles of titania, the platinum particles being in majority located in proximity to intergranular boundaries of the titania, the platinum particles being substantially smaller in size than the titania particles and being deposited thereon by: (a) immersion of the titania in a solution containing a platinum compound, the immersion taking place in an evacuated environment allowing entrapped air to be removed from the titania and allowing the solution to flow through the porous titania; (b) air drying the previously immersed titania; and (c) heating the air-dried titania in air for a time period and at a temperature sufficient to reduce the deposited platinum compound remaining after air drying of the solution to platinum particles and to sinter the platinum particles to the titania particles.
Claim 4
Dependent Claim
70 words
An improved sensor according to claim 1, wherein the titania ceramic element of the sensor has had the charge transfer material applied to the titania ceramic element by immersion of the titania ceramic element in a solution containing ions of the metal, the solution upon drying having formed deposits of a salt or compound, the salt or compound deposits having been decomposed to form the discontinuous metal charge transfer material.
Claim 5
Dependent Claim
22 words
An improved sensor according to claim 3, wherein the titania ceramic element, after its immersion in the solution, has been hot-air dried.
Claim 6
Dependent Claim
59 words
An improved sensor according to claims 3 or 4, wherein the titania ceramic element of the sensor has had the solution with the immersed titania ceramic element placed in an evacuated environment, thereby, to facilitate the removal of air from the porous titania ceramic element and to promote, thereby, dispersion of the solution throughout the porous titania ceramic element.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-10-14 | 1984-04-14 | 1984-10-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-10-14 | 1988-04-14 | 1988-10-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-10-14 | 1992-04-14 | 1992-10-14 | $7700.00 | Window Closed / Lapsed |