초록 ▼

A system for filtering and oxidizing particulate matter produced by a gasoline direct injection engine is disclosed. In one embodiment, engine cylinder air-fuel is adjusted to allow soot to oxidize at an upstream particulate filter while exhaust gases are efficiently processed in a downstream cataly

A system for filtering and oxidizing particulate matter produced by a gasoline direct injection engine is disclosed. In one embodiment, engine cylinder air-fuel is adjusted to allow soot to oxidize at an upstream particulate filter while exhaust gases are efficiently processed in a downstream catalyst.

대표청구항 ▼

1. A system for processing particulate matter of a gasoline engine having an exhaust system, comprising: a device including at least a first three-way catalyst and a particulate filter, said device being an aftertreatment device located farthest upstream in said exhaust system as compared to all oth

1. A system for processing particulate matter of a gasoline engine having an exhaust system, comprising: a device including at least a first three-way catalyst and a particulate filter, said device being an aftertreatment device located farthest upstream in said exhaust system as compared to all other aftertreatment devices in said exhaust system;a second three-way catalyst disposed in said exhaust system downstream of said device; anda controller, said controller substantially depleting an amount of oxygen in said first three-way catalyst before increasing a rate of oxidation of soot held by said particulate filter, said amount of oxygen depleted in response to an amount of soot held by said particulate filter exceeding a threshold. 2. The system of claim 1, further comprising said controller adjusting an air-fuel ratio of said gasoline engine during particulate filter regeneration so that exhaust gases flowing from the particulate filter are at stoichiometric conditions. 3. The system of claim 1, wherein said controller substantially depletes said amount of oxygen in said first three-way catalyst by enriching an air-fuel mixture of at least one cylinder of said gasoline engine. 4. The system of claim 3, wherein said at least one cylinder is a cylinder that is active during deceleration fuel shut-off or said at least one cylinder is a cylinder that is active during a variable displacement mode. 5. The system of claim 3, wherein said controller increases oxygen flow to said first three-way catalyst and to said particulate filter after substantially depleting said amount of oxygen by providing a lean air-fuel mixture to the at least one cylinder of said gasoline engine. 6. The system of claim 1, wherein the controller provides a lean air-fuel mixture after depleting the amount of oxygen in said first three-way catalyst until a threshold amount of oxygen is present in exhaust gases passing through said device. 7. The system of claim 1, wherein the controller increases a temperature of said particulate filter by retarding spark to said gasoline engine and by increasing air flow to said gasoline engine as part of a procedure to regenerate said particulate filter. 8. The system of claim 7, wherein said controller adjusts fuel delivered to said gasoline engine in response to a first oxygen sensor located upstream of said first three-way catalyst and in response to a second oxygen sensor located downstream of said particulate filter. 9. The system of claim 8, wherein said controller further adjusts said fuel delivered to said gasoline engine in response to a model that estimates the amount of stored soot and the rate of oxidation for said particulate filter. 10. A method for processing particulate matter of a gasoline engine, comprising: directing exhaust gases from said gasoline engine to a first three-way catalyst combined with a particulate filter and disposed in an exhaust system; andadjusting fuel delivered to said gasoline engine in response to an oxygen concentration in said exhaust system at a location upstream of said first three-way catalyst and upstream of a second three-way catalyst, the fuel delivered to said gasoline engine adjusted such that exhaust gas flowing from the particulate filter varies between rich and lean of stoichiometric conditions during particulate filter regeneration. 11. The method of claim 10, wherein said adjusting fuel delivered to said gasoline engine comprises richening an air-fuel mixture delivered to said gasoline engine when a temperature of said particulate filter exceeds a threshold and when an amount of soot held by said particulate filter exceeds a threshold amount, and leaning said air-fuel mixture delivered to said gasoline engine when said oxygen concentration in said exhaust system is less than a threshold amount in said exhaust system at a location downstream of said first three-way catalyst and upstream of said second three-way catalyst. 12. The method of claim 10, wherein said fuel delivered to said gasoline engine is enriched by increasing an amount of fuel injected to at least one cylinder during an engine operating condition where the particulate filter is being regenerated as compared to an amount of fuel injected to said at least one cylinder during a similar operating condition where said particulate filter is not being regenerated. 13. The method of claim 10, wherein said adjusting fuel delivered to said gasoline engine comprises leaning an air-fuel mixture delivered to said gasoline engine when a temperature of said particulate filter exceeds a threshold and when an amount of soot held by said particulate filter exceeds a first threshold amount, and richening said air-fuel mixture delivered to said gasoline engine when said oxygen concentration in said exhaust system is greater than a second threshold amount in said exhaust system at a location downstream of said first three-way catalyst and upstream of said second three-way catalyst. 14. The method of claim 10, wherein said adjusting fuel delivered to said gasoline engine further comprises adjusting said fuel delivered to said gasoline engine in response to an oxygen concentration at a location downstream of said second three-way catalyst. 15. The method of claim 10, wherein spark delivery to said gasoline engine is retarded from base timing before said adjusting fuel delivered to said gasoline engine, and said adjusting fuel delivered to said gasoline engine comprises alternating between richening and leaning an air-fuel mixture delivered to said gasoline engine in response to said oxygen concentration in said exhaust system at a location downstream of said first three-way catalyst and upstream of said second three-way catalyst, wherein said air-fuel mixture is richened or leaned by extending an amount of combustion events that at least one cylinder of said gasoline engine operates with a lean or rich air-fuel mixture. 16. A system for processing particulate matter of a gasoline engine having an exhaust system, comprising: a first three-way catalyst disposed in said exhaust system;a particulate filter disposed in said exhaust system at a location downstream of said first three-way catalyst;a second three-way catalyst disposed in said exhaust system downstream of said particulate filter; anda controller that adjusts fuel delivered to said gasoline engine in response to an oxygen concentration in said exhaust system at a location upstream of said first three-way catalyst and in response to an oxygen concentration in said exhaust system at a location downstream of said particulate filter to provide exhaust gases that vary between rich and lean of stoichiometric conditions. 17. The system of claim 16, wherein said controller further adjusts fuel delivered to said gasoline engine by leaning or richening an air-fuel mixture of at least one cylinder of said gasoline engine when an amount of soot held by said particulate filter exceeds a threshold amount and when a temperature of said particulate filter exceeds a threshold amount. 18. The system of claim 16, wherein an oxygen storage capacity of said first three-way catalyst is less than half an oxygen storage capacity of said second three-way catalyst. 19. The system of claim 16, wherein said controller further adjusts said fuel delivered to said gasoline engine to adjust an oxidation rate of soot held by said particulate filter, said oxidation rate increased by increasing a number of combustion events that at least one cylinder operates lean. 20. The system of claim 16, wherein an extent of leanness or richness of an air-fuel mixture of at least one cylinder is varied from rich to lean in relation to a desired rate of oxidation of soot held in said particulate filter. 21. The system of claim 19, wherein the number of combustion events said at least one cylinder is operated lean is related to a desired rate of oxidation of soot held by said particulate filter. 22. The system of claim 16, wherein a duty cycle between rich and lean air-fuel mixtures combusted by at least one cylinder is related to a desired rate of oxidation of soot held by said particulate filter. 23. A method for processing particulate matter of a gasoline engine, comprising: directing exhaust gases from said gasoline engine to a first three-way catalyst;directing exhaust gases from said first three-way catalyst to a particulate filter;directing exhaust gases from said particulate filter to a second three-way catalyst; andadjusting fuel delivered to said gasoline engine such that said first three-way catalyst and said second three-way catalyst are operated at substantially stoichiometric conditions when an amount of soot held by said particulate filter is less than a threshold; andadjusting fuel delivered to said gasoline engine such that said first three-way catalyst is operated rich and lean about stoichiometric conditions while said second three-way catalyst is operated rich and lean about stoichiometric conditions when the amount of soot held by said particulate filter is greater than said threshold. 24. The method of claim 23, wherein an air-fuel mixture produced by said fuel delivered to at least one cylinder of said gasoline engine is leaned when the amount of soot held by said particulate filter exceeds the threshold. 25. The method of claim 23, wherein said fuel delivered to said gasoline engine is varied from rich to lean in relation to a desired rate of oxidation of soot held in said particulate filter. 26. The method of claim 23, wherein an amplitude between rich and lean air-fuel ratio mixtures that are delivered to said gasoline engine is related to a desired rate of oxidation of soot held in said particulate filter.