Patent Application
20200319138
The present disclosure relates to an oxygen sensor. More specifically, the present disclosure relates to an oxygen sensor with uniform catalyst distribution.
Many motor vehicles are powered by internal combustion engines. These engines typically include an oxygen sensor that measures the oxygen content of the exhaust gases. These measurements are forwarded to, for example, a controller that regulates the air/fuel mixture and exhaust gas emissions of the engine.
During the fabrication of an oxygen sensor, an alumina coating is applied to a substrate and the coating is dipped into a catalyst solution. The sensor is subsequently heated internally to dry the catalyst solution. During the drying process, however, the catalyst particles tend to migrate to the source of heat in the sensor. As such, the distribution of the catalyst particles in the alumina coating is non-uniform. Non-uniform agglomeration of the catalyst particles leads to sintering of the particles during the use of the sensor, resulting in declined catalytic activity and reduced durability of the sensor.
Thus, while current oxygen sensors achieve their intended purpose, there is a need for a new and improved sensor and fabrication process to provide a sensor that eliminates or reduces sintering effects and, hence, promotes improved performance and durability.
According to several aspects, an oxygen sensor for a motor vehicle includes a substrate and an alumina coating covering the substrate, palladium (Pd) and platinum (Pt) catalyst particles being uniformly distributed in the alumina coating. The substrate includes a first ceramic layer including a Nernst cell, a second ceramic layer including a reference cell, a third ceramic layer, the second ceramic layer positioned between the first ceramic layer and the third ceramic layer, a heater element positioned between the second ceramic layer and the third ceramic layer.
In an additional aspect of the present disclosure, the Nernst cell is defined by a first electrode and a second electrode spaced apart from the first electrode.
In another aspect of the present disclosure, the first electrode and the second electrode are made of Pt.
In another aspect of the present disclosure, the reference cell is a hollow region in the second ceramic layer to provide a channel for gas flow.
In another aspect of the present disclosure, a catalyst particles or precursor solution is premixed in an alumina slurry that is sprayed onto the substrate to form the alumina coating.
In another aspect of the present disclosure, the catalyst precursor solution is nitrate based including Pd(NO3)2 and Pt(NO3)4 or chloride based including PdCl2 and PtCl2.
In another aspect of the present disclosure, an alumina slurry is sprayed onto the substrate to form the alumina coating which is subsequently dipped into a catalyst precursor solution.
In another aspect of the present disclosure, the catalyst precursor solution is nitrate based including Pd(NO3)2 and Pt(NO3)4 or chloride based including PdCl2 and PtCl2.
In another aspect of the present disclosure, an external heater is activated to dry the alumina slurry with the Pd/Pt precursors.
In another aspect of the present disclosure, the alumina coating fully covers the substrate.
According to several aspects, a method of forming an oxygen sensor implemented in a motor vehicle includes applying an alumina slurry covering a substrate, palladium (Pd) and platinum (Pt) catalyst particles or precursors being uniformly distributed in the alumina slurry, and heating the alumina slurry to form an alumina coating with uniformly distributed Pd and Pt catalyst particles. The substrate includes a first ceramic layer with a Nernst cell, a second ceramic layer with a reference cell, and a third ceramic layer, the second ceramic layer positioned between the first ceramic layer and the third ceramic layer, and a heater element positioned between the second ceramic layer and the third ceramic layer.
In another aspect of the present disclosure, the Nernst cell is defined by a first electrode and a second electrode spaced apart from the first electrode.
In another aspect of the present disclosure, the reference cell is a hollow region in the second ceramic layer to provide a channel for gas flow.
In another aspect of the present disclosure, a catalyst particles or precursor solution is premixed in the alumina slurry that is sprayed onto the substrate to form the alumina coating.
In another aspect of the present disclosure, the catalyst precursor solution is nitrate based including Pd(NO3)2 and Pt(NO3)4 or chloride based including PdCl2 and PtCl2.
In another aspect of the present disclosure, the alumina slurry is sprayed onto the substrate to form the alumina coating which is subsequently dipped into a catalyst precursor solution.
In another aspect of the present disclosure, the catalyst precursor solution is nitrate based including Pd(NO3)2 and Pt(NO3)4 or chloride based including PdCl2 and PtCl2.
In another aspect of the present disclosure, heating includes heating with an external heater that is activated to dry the alumina slurry with the Pd/Pt particles/precursors.
In another aspect of the present disclosure, the alumina coating fully covers the substrate.
According to several aspects, an oxygen sensor for a motor vehicle includes a substrate and an alumina coating covering the substrate, palladium (Pd) and platinum (Pt) catalyst particles being uniformly distributed in the alumina coating. The substrate includes a first ceramic layer including a Nernst cell, the Nernst cell being defined by a first electrode and a second electrode spaced apart from the first electrode, the first electrode and the second electrode being made from Pt; a second ceramic layer including a reference cell, the reference cell being a hollow region in the second ceramic layer to provide a channel for gas flow; a third ceramic layer, the second ceramic layer positioned between the first ceramic layer and the third ceramic layer; and a heater element positioned between the second ceramic layer and the third ceramic layer.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
Referring to
Referring further to
During the fabrication of the sensor 10, the Pd and Pt catalyst particles are synthesized from Pd and Pt precursors. The Pd and Pt catalyst particles are then mixed with an alumina slurry, which is subsequently sprayed onto the substrate 17, for example, utilizing thermal spraying.
The sensor 10 formed by the aforementioned process is in contrast to a sensor 11 (
Accordingly, the process associated with the sensor 10 shown in
In another arrangement, in accordance with the principles of the present invention, the sensor 10 is formed by an alternative process by first thermal spraying an alumina slurry onto the substrate 17 to form an alumina coating and then dipping the coating in a catalyst solution of nitrate based catalyst precursors Pd(NO3)2 and Pt(NO3)4. The nitrate based catalyst precursors dry and decompose at lower temperatures than a chloride based precursor solution typically associated with the fabrication of the sensor 11 shown in
Referring now to
In various arrangements, Pd and Pt precursors are first processed to obtain Pd/Pt particles which are then mixed with the alumina slurry. In certain arrangements, the alumina slurry is mixed with Pd/Pt precursors. The slurry is then heated to form Pt/Pd particles in the alumina slurry.
The description of the present disclosure is merely exemplary in nature and variations that do not depart from the gist of the present disclosure are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.
