Catalytic converter optimization

A catalytic converter includes an inlet. A first sub-section of substrate is located a first distance from the inlet that includes a first catalyst coating having a first density. A second sub-section of substrate is located a second distance from the inlet that includes a second catalyst coating having a second density. The second distance is greater than the first distance and the second density is greater than the first density.

FIELD

The present disclosure relates to catalytic converters.

BACKGROUND

Automobile engines produce emissions such as carbon monoxide (CO), volatile organic compounds (VOCs), and nitrogen oxides (NOx). An automobile may include one or more catalytic converters that are designed to reduce these emissions. A catalytic converter includes a plurality of substrates coated with catalysts, such as precious group metals like platinum, rhodium and/or palladium. The structure is designed to expose a maximum surface area of the catalysts to exhaust flowing from the engine thus, reducing a level of emissions in the exhaust through chemical reactions with the catalysts.

Conventional catalytic converters provide a higher density of catalysts in a forward section of the catalytic converter to increase the reduction of emissions. At the same time, conventional converters provide a lower density of catalysts in a distal section of the catalytic converter to decrease cost. More particularly, with reference toFIG. 1, a catalytic converter10according to the prior art is shown. The catalytic converter10includes an inlet12that allows exhaust14to enter the catalytic converter10and an outlet16that allows exhaust14to exit the catalytic converter10.

The catalytic converter10includes a first substrate18arranged in a first sub-section20of the catalytic converter10and a second substrate22arranged in a second sub-section24of the catalytic converter10. The first substrate18includes a first catalyst coating26. The catalyst coating26is evenly distributed at a first density throughout the first substrate18. The coating26generally includes oxidation catalysts such as platinum and palladium. The second substrate22includes a second catalyst coating28. The second catalyst coating28is evenly distributed throughout the second substrate22at a second density that is less than the first density. The second coating28generally includes oxidation and reduction catalysts such as platinum, palladium and rhodium.

This design is a viable trade-off for catalytic converters with lower exhaust temperatures and more lenient emissions standards. With the advent of catalytic converters mounted closer to the engine, resulting in higher exhaust temperatures and faster catalyst warm-up rates, the higher density of catalysts on the front section adds minimal reduction in emissions. Stricter emissions standards generate a need for a greater reduction in emissions without a large increase in the amount of Precious Metals added to the catalysts.

SUMMARY

In view of the above, the present disclosure teaches a catalytic converter. The catalytic converter includes an inlet. A first sub-section of substrate is located a first distance from the inlet that includes a first catalyst coating having a first density. A second sub-section of substrate is located a second distance from the inlet that includes a second catalyst coating having a second density. The second distance is greater than the first distance and the second density is greater than the first density.

In other features, a method of forming a catalytic converter is provided. The method includes: dividing at least one substrate structure into a plurality of sub-sections; coating a first sub-section of the plurality of sub-sections with a first density of catalysts; coating a second sub-section of the plurality of sub-sections with a second density of catalysts greater than the first density; providing the first sub-section within a first distance from an inlet of the catalytic converter; and providing the second sub-section within a second distance greater than the first distance from the inlet.

DETAILED DESCRIPTION

Referring now toFIG. 2, a vehicle30includes a control module32, an engine34, a fuel system36, and an exhaust system38. A throttle40communicates with the control module32to control air flow into an intake manifold35of the engine34. The amount of torque produced by the engine34is proportional to mass air flow (MAF) into the engine34. The engine34operates in a lean condition (i.e. reduced fuel) when the A/F ratio is higher than a stoichiometric A/F ratio. The engine34operates in a rich condition when the A/F ratio is less than the stoichiometric A/F ratio. Internal combustion within the engine34produces exhaust gas that flows from the engine34to the exhaust system38, which treats the exhaust gas and releases the exhaust gas to the atmosphere. The control module32communicates with the fuel system36to control the fuel supply to the engine34.

The exhaust system38includes an exhaust manifold42, a catalytic converter44, and one or more oxygen sensors46,48. The catalytic converter44controls emissions by increasing the rate of oxidation of hydrocarbons (HC) and carbon monoxide (CO) and the rate of reduction of nitrogen oxides (NOx). The catalytic converter44requires oxygen. The oxygen sensor46, measures the amount of oxygen entering the catalyst, and oxygen sensor48provides feedback to the control module32indicating a level of oxygen in the exhaust. Based on the oxygen sensor signals, the control module32controls air and fuel at a desired air-to-air (A/F) ratio to provide optimum engine performance as well as to provide optimum catalytic converter performance.

Referring now toFIG. 3, an exemplary catalytic converter44according to various embodiments is shown. According to the present disclosure, catalyst coatings within the catalytic converter are distributed in sub-sections at varying densities optimized by catalyst temperature and catalyst activation temperature. In other words, densities of the catalyst coatings are varied according to an operating temperature of the catalytic converter to optimize efficiency. For example, since the improvement in catalyst conversion efficiency diminishes for temperatures far above the activation temperature, the density of the first coating is reduced where the temperature of the catalytic converter is much greater than a catalyst activation temperature. Conversely, the density of the second coating is increased where the temperature of the catalytic converter is lower. As can be appreciated, varying the density of the catalyst coatings according to the present disclosure can be applied to catalytic converters including one or more substrate structures. As also can be appreciated, the densities of the catalyst coatings can be applied in a step-like format or a continuous or linear format.

As shown inFIG. 3, an exemplary catalytic converter44includes an inlet46that allows the exhaust to enter the catalytic converter44and an outlet48that allows the exhaust to exit the catalytic converter44. The catalytic converter44further includes at least two substrate structures50,52. The substrate structures50,52may include a ceramic structure formed in one of a honeycomb structure, a bead structure, or the like. The physical properties of the two substrate structures may also vary depending on the intended functions. The first substrate structure50further includes a first sub-section54and a second sub-section56. The first sub-section54is located a first distance from the inlet46. The second sub-section56is located a second distance from the inlet46that is greater than the first distance. The first sub-section54within the first substrate structure50is coated with catalysts at a first density. The first coating can include an oxidation catalyst that reduces Hydrocarbon and Carbon Monoxide emissions. The oxidation catalyst includes, but is not limited to, palladium, platinum, and/or the like. The second sub-section56within the first substrate structure50is coated with catalysts at a second density. The second density is greater than the first density. The second coating can include an oxidation catalyst that reduces Hydrocarbon and Carbon Monoxide emissions, as discussed above, and it may also include a NOx reduction catalyst, such as rhodium.

The second substrate structure52further includes a first sub-section58and a second sub-section60. The first sub-section58is located a third distance from the inlet46. The third distance is greater than the second distance. The second sub-section60is located a fourth distance from the inlet46. The fourth distance is greater than the third distance. The first sub-section58of the second substrate structure52includes a third coating of catalysts coated according to a third density that is less than or equal to the second density. The third coating can include both oxidation and reduction catalysts that simultaneously reduce CO, Hydrocarbon and NOx emissions. The catalysts include, but are not limited to, platinum, palladium, rhodium and/or the like. The second sub-section60of the second substrate structure52includes a fourth coating of catalysts coated according to a fourth density that is less than the first, second, and third densities.

With continued reference toFIG. 3and referring now toFIG. 4, a graph illustrates catalyst temperature and conversion efficiency data during a first acceleration cycle. Catalyst temperature is shown along the left y-axis at62. Conversion efficiency is shown along the right y-axis at64. Catalyst conversion efficiency data at points A, B, C, D, and E along the center axis (Y) of the catalytic converter10according to the prior art is shown at66. Catalyst conversion efficiency data at substantially similar points A, B, C, D and E along the center axis (Y) of the catalytic converter44ofFIG. 3is shown at68. The catalyst temperature data is shown at70. The increased densities in sub-sections between points B and D provide for a greater conversion efficiency at the same catalyst temperature as shown at72. Increasing the density of catalysts in sub-sections based on the catalyst temperature decreases the catalyst light-off or activation temperature.

To further illustrate a catalytic converter of the present disclosure, an exemplary method for coating substrate structures to be formed within a catalytic converter is shown inFIG. 5. As can be appreciated, steps of the method can be performed in varying order. Therefore, the present disclosure is not limited to the sequential execution as shown inFIG. 5. The exemplary method is generally shown at80. The exemplary method may begin at82. A first sub-section of the substrate structure is determined at84. The area of the first sub-section can be determined based on at least one of catalyst temperature and catalyst activation temperature. The first sub-section of the substrate structure is coated with a first catalyst coating according to a first density at86. A second sub-section of the substrate structure is determined at88. The area of the second sub-section can be determined based on at least one of catalyst temperature and catalyst activation temperature. The second sub-section of the substrate structure is coated with a second coating according to a second density that is greater than the first density at90. The substrate structure is formed at a first distance from an inlet of the catalytic converter at92.

A first sub-section of a second substrate structure is determined at94. The area of the first sub-section can be determined based on at least one of catalyst temperature and catalyst activation temperature. The first sub-section of the second substrate structure is coated with a third catalyst coating according to a third density at96. A second sub-section of the second substrate structure is determined at98. The area of the second sub-section can be determined based on at least one of catalyst temperature and catalyst activation temperature. The area of the second sub-section can be less than the area of the first sub-section. The second sub-section of the second substrate structure is coated with a fourth catalyst coating according to a fourth density at100. The fourth density is less than the third density. The second substrate structure is formed a second distance from the inlet of the catalytic converter at102. The second distance is greater than the first distance. The method ends at104.

Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, while this disclosure has been described in connection with particular examples thereof, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification, and the following claims.