Exhaust emission reduction system having an HC-trap and NOx-trap combination designed for operating under strategic lean conditions

Patent metadata

Field	Value
Publication number	US-10781735-B2
Application number	US-201815983300-A
Country	US
Kind code	B2
Filing date	May 18, 2018
Priority date	May 18, 2018
Publication date	Sep 22, 2020
Grant date	Sep 22, 2020

Abstract

Methods and systems are featured for reducing harmful exhaust gas components of combustion devices such as gasoline-powered combustion engines (e.g., predominately stoichiometric running engines). The methods and systems include an underbody combination of a hydrocarbon trap (HCT), suited for cold start hydrocarbon adsorption, as well as an associated NOx trap. The system is inclusive of a control unit for extending a lean exhaust condition reaching the desorbing HCT as to avoid a deficiency in oxygen during the time period of HCT desorption. The system is also inclusive of one or more TWCs as in one associated with the underbody HCT-NOx-trap combination and/or one positioned in a close coupled position. Platinum group metals as in Pd, Rh and Pt are also featured on one, two or all three of the HCT, NOx-trap, and TWC when present.

First claim

What is claimed is:

1. An exhaust emission reduction system suited for use with a gasoline running engine, comprising:
an exhaust treatment apparatus having an underbody positioned NOx-trap and HC-trap combination;
a control unit operable to extend a lean exhaust condition into a period of desorption of hydrocarbons trapped by the HC-trap as to promote hydrocarbon emission reduction during the desorption period.

2. The system of claim 1 wherein the NOx-trap and HC-trap combination includes a substrate support onto which the HC-trap is layered and over which HC-trap layer the NOx-trap is layered.

3. The system of claim 1 wherein the exhaust treatment apparatus further comprises one or more TWC components.

4. The system of claim 3 wherein the exhaust treatment apparatus comprises both an upstream close coupled TWC component and a downstream, underbody TWC component, with the downstream TWC being in a common support canister with NOx-trap and HC-trap components of the NOx-trap and HC-trap combination.

5. The system of claim 3 wherein the NOx-trap and HC-trap combination includes a substrate support onto which the HC-trap is layered and over which HC-trap layer the NOx-trap is layered, and wherein the one or more TWC components includes a TWC component positioned downstream of the NOx-trap and HC-trap combination.

6. The system of claim 1 wherein the exhaust treatment apparatus includes a close coupled TWC and the NOx-trap and HC-trap combination includes an upstream underbody NOx-trap on a first support substrate and a second support substrate which supports an HC-trap layer and a TWC layer over the HC-trap layer.

7. The system of claim 1 wherein the exhaust treatment apparatus includes a first support substrate with an HC-trap layer with PGM material, and over which the HC-trap layer is supplied with one or both of a NOx-trap layer and a TWC layer.

8. The system of claim 7 wherein only a TWC layer is supplied over the HC-trap layer and a second support substrate is positioned downstream of the first support substrate, and with the second support substrate supporting the NOx-trap layer of the NOx-trap and HC-trap combination.

9. The system of claim 7 wherein both the TWC layer and the NOx-trap layer are provided over the HC-trap layer so as to be supported on the first support substrate.

10. The system of claim 9 wherein at least a portion of the TWC layer is positioned upstream of a downstream end of the NOx-trap layer.

11. The system of claim 9 wherein at least a portion of the TWC layer is positioned downstream of an upstream end of the NOx-trap layer.

12. The system of claim 1 wherein the exhaust treatment apparatus includes a first support substrate which supports a first HC-trap zone and a second zone occupied by one of (a) and (b), with (a) being the NOx trap and (b) a TWC layer, and over which first and second zones supported by the first support substrate is provided an over covering of one of (a) or (b), with the over covering being the (a) or (b) not representing the second zone.

13. The system of claim 12 wherein the HC-trap zone comprises a PGM which includes Pd and a transition metal and/or P-block metal component.

14. The system of claim 12 wherein (a) is provided as the second zone, and which second zone is upstream of the HC-trap zone, and (b) extends over each of (a) and the HC-trap zone.

15. The system of claim 12 wherein (a) is provided as the second zone, and which second zone is downstream of the HC-trap zone, and (b) extends over each of (a) and the HC-trap zone.

16. The system of claim 12 wherein (b) is provided as the second zone, and which second zone is downstream of the HC-trap zone, and (a) extends over each of (b) and the HC-trap zone.

17. The system of claim 1 wherein the control unit receives input sensing information and/or modeling information of HC desorption characteristics and extends a period of lean exhaust supply to the HC-trap layer during a period of desorption of the HC-trap based on the received information.

18. The system of claim 1 wherein the control unit sets a time period or system temperature parameter which ensures a lean exhaust supply to the HC-trap layer at a time when the HC-trap layer is desorbing hydrocarbons, and optionally the control unit receives feedback monitoring information as to desorption characteristics or desorption period timing relative to the HC-trap.

19. The system of claim 1 wherein the control unit sets an extended period of time or temperature range end point, after a prior cold start period, wherein lean exhaust flow is provided to the desorbing HCT before returning to a predominately stoichiometric exhaust flow over the HC-trap.

20. The system of claim 1 further comprising an engine of either a hybrid or non-hybrid form, which engine is selected from the group consisting of port-fuel injection (PFI) engines, stratified charge engines (SCE), gasoline direct engines (GDI), dual injection system engines (PFI+GDI), and gasoline direct injection compression ignition (GDCI) engines.

21. The system of claim 1 wherein, relative to an entire length from an engine exhaust output to a release point of that exhaust to the atmosphere, there is lacking a dedicated SCR catalyst unit.

22. The system of claim 1 wherein the control unit includes a signal transmitting component, with the signal transmitting component including a signaling device that retains an extended period of lean exhaust flow over the HC-trap and NOx-trap combination receiving exhaust output from the predominately stoichiometric running gasoline engine which, but for the control unit signaling, would calibrate to a predominately stoichiometric lambda setting.

23. A method of reducing exhaust emissions comprising passing exhaust over the exhaust treatment apparatus in the exhaust emission reduction system of claim 1 .

24. The system of claim 1 wherein the exhaust treatment apparatus is free of communication with a SCR in either an upstream or downstream exhaust flow direction.

25. The system of claim 24 wherein the HC-trap is supported on a first support substrate together with at least one of the NOx-trap material and a TWC material.

26. The system of claim 25 , further comprising a canister and wherein all three of the HC-trap, NOx-trap, and TWC are in the canister.

27. The system of claim 1 wherein the extension of the lean exhaust condition by the control unit involves a continuous maintenance of the lean exhaust state from a point of initiation of the lean state for hydrocarbon emission reduction by the exhaust treatment apparatus until completion of a full period of desorbing hydrocarbon emission reduction by the exhaust treatment apparatus.

28. The system of claim 1 wherein the lean exhaust condition extension is stopped by the control unit upon a determination by the control unit that the extension is sufficient to reduce all hydrocarbon desorption from the HC-Trap.

Assignees

• Umicore Ag & Co Kg

Inventors

• Moser David
• Nunan John
• Alltizer Chad

Classifications

• B01D2255/904

  Multiple catalysts · CPC title

• F01N2590/11

  for hybrid vehicles · CPC title

• B01D2255/9022

  Two layers · CPC title

• F01N2510/0682

  having a discontinuous, uneven or partially overlapping coating of catalytic material, e.g. higher amount of material upstream than downstream or vice versa · CPC title

• B01D2255/9155

  Wall flow filters · CPC title